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Selected Abstracts from the Thirty-fourth Annual Meeting of the Scandinavian Society for Electron Microscopy SCANDEM-81
Ultramicroscopy 6 (1981) 409-417 North-Holland Publishing Company
Selected Abstracts from the
T h i r t y - f o u r t h Annual M e e t i n g of The S c a n d i n a v i a n Society for E l e c t r o n M i c r o s c o p y
SCANDEM-81
D e p a r t m e n t of P a t h o l o g y Huddinge Hospital Stockholm 3-5 June 1981
The S c a n d i n a v i a n Society for E l e c t r o n M i c r o s c o p y h e l d its 34th annual meeting, SCANDEM-81, in S t o c k h o l m on 3-5 June 1981. F r o m over 290 participants, the o r g a n i z e r s have s e l e c t e d a number of abstracts concerning m a t e r i a l s science w h i c h should be of i n t e r e s t to U ! t r a m i c r o s c o p y ' s readers. (The b i o l o g i c a l aspects of the S C A N D E M - 8 1 p r o g r a m w i l l appear later in J o u r n a l of U l t r a s t r u c t u r e Research.)
Bj~rn V. J o h a n s e n
0304-3991/81/0000-0000/$02.50 © 1981 North-Holland
Abstracts of 34th Scandinavian SocieO; Annual Meet#zg E L E C T R O N M I C R O S C O P Y IN MATERIALS SCIENCE
5. 6.
A P P L I C A T I O N OF E L E C T R O N M I C R O S C O P Y IN THE STUDY OF P O L Y M E R C R Y S T A L L I Z A T I O N AND IN THE QUEST OF A C H I E V E M E N T OF DESIRABLE PROPERTIES A.
Keller H. H. W i l l s P h y s i c s L a b o r a t o r y , U n i v e r s i t y o f B r i s t o l , R o y a l Fort, T y n d a l l A v e n u e , B r i s t o l BS8 ITL, U.K.
The e m p h a s i s of the lecture is twofold. F i r s t it is to d e m o n s t r a t e the p o w e r of p r i m a r y real space imaging in the much d i s p u t e d area of how l o n g - c h a i n po l y m e r s o r g a n i z e t h e m s e l v e s to form crystals, with due e v a l u a t i o n of all p r i n c i p a l e v i d e n c e and of the t e c h n i c a l ities i n v o l v e d (on the much d i s p u t e d problem of how r e g u l a r l y and a d j a c e n t l y the chains fold up along the g r o w i n g crystal face as o p p o s e d to m e r e l y 'freezing in' from the r a n d o m state, see ref. i). Secondly, it will be d e m o n s t r a t e d on a few s e l e c t e d e x a m p l e s of how the study of e l e c t r o n m i c r o s c o p i c m o r p h o l o g y , w h e n applied at the right stage, in the right c o m b i n a t i o n w i t h o t h e r techniques, can d e c i s i v e l y further the a c h i e v e m e n t of high m o d u l u s and high strength, w h i c h is i n t r i n s i c to the v a l e n c e b o n d e d long chain molecule, but n o t usually a c h i e v e d in c o n v e n t i o n a l t e c h n o l o g i c a l practice. In this latter r e s p e c t fibrous c r y s t a l l i zation in p r e o r i e n t e d s o l u t i o n s and melts leading to the s o - c a l l e d 'shish-kebabs' and 'row structures' w i l l be d i s c u s s e d 2-~ t o g e t h e r w i t h a p a r t i c u l a r e x a m p l e of 'morphological engineering' w h e r e a predominantly platelet-containing structure a p p r o p r i a t e l y i n i t i a t e d by fibres has a p a r t i c u l a r l y b e n e f i c i a l e f f e c t on promoting s t i f f n e s s 5. The last case also provides an e x p l a n a t i o n in m o r p h o l o g i c a l terms of why and how certain o r i e n t e d p o l y m e r s may improve their s t i f f n e s s on storage6, 7 .It is h o p e d that the latter examples, b e s i d e s b e i n g i n s t r u c t i v e for the e l e c t r o n m i c r o s c o p y of polymers, may also o f f e r some t e c h n o l o g i c a l g u i d e l i n e s in the a c h i e v e m e n t and p r o d u c t i o n of o r i e n t e d fibres and films w i t h advantageous properties. I. 2. 3.
4.
Faraday Discussion No. 68 (1979), see Introduction by A. Keller, p. 145. A. Keller, J. Polymer Sci. Polymer Symposia 58 (1977) 395. A. Keller, in Ultra-high modulus polymers (ed. A. Cifferi and I. M. Ward), Appl. Sci. Publishers, 1979. A. Keller and P. J. Barham, Plastics and Rubber International 6 (1981) 19.
7.
411
J. A. Odell, D. T. Grubb and A. Keller, Polymer 19 (1978) 617. R. G. C. Arridge, P. J. Barham and A. Keller, J. Polymer Sci. Polymer Phys. ed. 15 (1977) 389. J. A. Odell, A. Keller and M. Miles, to be published.
THE T R A N S M I S S I O N E L E C T R O N A CHEMICAL LABORATORY
MICROSCOPE
AS
K. E. E a s t e r l i n g D e p a r t m e n t of E n g i n e e r i n g M a t e r i a l s , U n i v e r s i a of L u l e ~ , S w e d e n
The most i m p o r t a n t d e v e l o p m e n t in e l e c t r o n m i c r o s c o p y in recent years has u n d o u b t e d l y been the i n t r o d u c t i o n of c o m b i n e d T E M / S T E M systems. This c o m b i n a t i o n allows us to retain all the a d v a n t a g e s of high r e s o l u t i o n m i c r o s c o p y of c o n v e n t i o n a l t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y t o g e t h e r w i t h the p o s s i b i l i t i e s of u s i n g the i n s t r u m e n t as a high r e s o l u t i o n e l e c t r o n m i c r o probe. In addition, the d i g i t i z e d image of the S T E M / S E M TV d i s p l a y can be u t i l i z e d for p a r t i c l e analysis w o r k or i n c o n j u n c t i o n w i t h in-situ d e f o r m a t i o n experiments. In o t h e r words, w i t h i n the the one system, most of the facilities of a c h e m i c a l / m a t e r i a l s testing laboratory are available. E x a m p l e s of how such a s o p h i s t i c a t e d s y s t e m c o n t a i n i n g (TEM-STEM-PASTEM-EDX-EELS-in-situ d e f o r m a t i o n stage), etc. can be used to help solve m a t e r i a l s p r o b l e m s are shown in the talk.
MATERIAL Lars-Eric
ANALYSIS
WITH
PIXE
Carlsson
Dept. o f N u c l e a r P h y s i c s , L u n d I n s t i tute o f T e c h n o l o g y , S o l v e g a t . 14, S - 2 2 3 62 Lund, S w e d e n
Method: In P I X E - a n a l y s i s (ParticleI n d u c e d X - r a y Emission) samples are i r r a d i a t e d w i t h p r o t o n s or h e a v i e r ions a c c e l e r a t e d in a p o t e n t i a l of 1-5 MV. The i n d u c e d X - r a y s are d e t e c t e d in an e n e r g y - d i s p e r s i v e s o l i d state detector. The m e t h o d is u s u a l l y a p p l i e d to e i t h e r thin or thick samples (< 1 m g / c m 2 and < 15 m g / c m 2 r e s p e c t i v e l y ) . The X - r a y b a c k g r o u n d in P I X E - a n a l y s i s is 3 to 4 o r d e r s of m a g n i t u d e lower than in e l e c t r o n - i n d u c e d analysis and the d e t e c t i o n limits a t t a i n a b l e w i t h irradi a t i o n times of a few m i n u t e s lies in the 0.5 - 5 p p m region for m a n y e l e m e n t s X - r a y a n a l y s i s can be done for all
Abstracts of 34th Scandinavian SocieO, Annual Meeting
412
elements h e a v i e r ~han Mg and by simultaneous d e t e c t i o n of particles or gammarays from n u c l e a r reactions many lighter elements may also be analysed. By using an a u t o m a t i c sample changer and a p o w e r f u l c o m p u t e r code with simultaneous fitting of b a c k g r o u n d and all X-ray peaks for up to 35 elements it is p o s s i b l e to p e r f o r m rapid, low-cost analysis of a large n u m b e r of samples. Thick samples: The most common means of e x c i t a t i o n is to use protons in the 2-3 M e V range. When a n a l y s i n g thick samples this e x c i t a t i o n allows for the d e t e c t i o n of Li, B, F, Na, M g and A1 by d e t e c t i n g gamma-rays from n u c l e a r reactions. This is done s i m u l t a n e o u s l y with X - r a y analysis of all h e a v i e r elements. In this w a y p r a c t i c a l l y all m a t r i x elements are m e a s u r e d and accurate thick target c o r r e c t i o n s b a s e d on f u n d a m e n t a l p a r a m e t e r s can be performed. This technique is p r e s e n t l y b e i n g s u c c e s s f u l l y applied to the analysis of both geological and b i o l o g i c a l material. The irradiation area used in these b r o a d b e a m analyses is u s u a l l y b e t w e e n 5 and 50 m m 2. Microbeam: The P I X E - m e t h o d is also very useful in m i c r o a n a l y s i s . Beam-spot diameters b e l o w 100 ~m can be a c h i e v e d by simply c o l l i m a t i n g the p a r t i c l e beam. With both c o l l i m a t i o n and focusing, beamspot sizes b e t w e e n 1 - i0 ~m d i a m e t e r may be obtained. B e a m current l i m i t a t i o n s increase the d e t e c t i o n limits a p p r o x i m a t e l y a factor of 10 c o m p a r e d to b r o a d b e a m analysis. Lateral d i s t r i b u t i o n s of d i f f e r e n t e l e m e n t s can be a c h i e v e d by s c a n n i n g the sample w i t h s t e p - m o t o r s or by s c a n n i n g the p a r t i c l e b e a m w i t h an e l e c t r o s t a t i c or m a g n e t i c sweep system. The m i c r o b e a m setup in Lund is, in its p r e s e n t status, capable of p r o d u c i n g b e a m spots down to 15 ~m diameter.
INDUSTRIAL P.-E.
APPLICATIONS
OF AES
Nilsson-Jatko
ASEA
AB,
72183
Vaster~s,
Sweden
Scanning Auger electron spectroscopy has p r o v e d to be a v e r s a t i l e t e c h n i q u e for s o l v i n g a wide range of m a t e r i a l problems. The e x c e l l e n t depth r e s o l u t i o n and the high lateral r e s o l u t i o n in combination with the ability to detect all e l e m e n t s with z ~ 3 make it a s t r o n g analytical instrument. This w i l l be illustrated w i t h examples from d e v e l o p m e n t projects w h e r e the AES t e c h n i q u e has been app l i e d and from p r o d u c t i o n p r o b l e m s involving c o n t a m i n a t e d surfaces, i n s u f f i c i e n t a d h e s i o n and m a t e r i a l e m b r i t t l e m e n t . As an introduction, p r i n c i p l e s of AES and ins t r u m e n t p e r f o r m a n c e are b r i e f l y covered.
AN A P P R O A C H DIFFRACTION
TO C O M B I N E X-RAY, EELS AND M I C R O A N A L Y S I S IN TEM
P. H a g e m a n n N. V. P h i l i p s ' G l o e i l a m p e n f a b r i e k e n , S & I Electron Optics Applications Laboratory, B u i l d i n g T Q I I I - p , 5600 MD Eindhoven, The N e t h e r l a n d s .
The a n a l y t i c a l t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y utilises the t e c h n i q u e s of X-ray analysis, e l e c t r o n energy loss s p e c t r o s c o p y and e l e c t r o n d i f f r a c t i o n to c h a r a c t e r i s e and analyse m i c r o - a r e a s and c o m p l e m e n t the b a s i c image information. It is of i n t e r e s t to note that the problems of q u a n t i f i c a t i o n of the i n f o r m a t i o n a v a i l a b l e to the user has reached different levels for each of the above methods. X-ray analysis has made the most p r o g r e s s over the last decade because of e x t e n s i v e t e c h n o l o g i c a l and app l i c a t i o n s effort. E l e c t r o n e n e r g y loss s p e c t r o s c o p y is c u r r e n t l y p o s s i b l e w i t h good r e s o l u t i o n in compact s p e c t r o m e t e r s and may in the future attain status as a routine tool in e l e m e n t a l analysis and with approp r i a t e e l e c t r o n optics a v a i l a b l e in all modes (TEM, STEM, (micro-) d i f f r a c t i o n ) . The third m e t h o d mentioned, e l e c t r o n diffraction, has r e c e i v e d an e x t e n s i o n to its a p p l i c a t i o n range since the introduction of m i c r o d i f f r a c t i o n to routine TEM work. Data a c q u i s i t i o n and q u a n t i f i cation of the e l e c t r o n d i f f r a c t i o n , however, has r e c e i v e d little a t t e n t i o n to date. The p h o t o g r a p h i c e m u l s i o n is still c o n s i d e r e d the s t a n d a r d r e g i s t r a t i o n medium. The a t t e n d a n t tedious p r o c e s s i n g r e q u i r e d to o b t a i n d i f f r a c t i o n data from it is a c c e p t e d as normal. This attitude is in obvious c o n t r a d i c t i o n to the current p r o g r e s s in the a u t o m a t i o n and d e v e l o p m e n t of q u a n t i t a t i v e X - r a y diff r a c t i o n analysis p r o c e s s e s . To redress this s i t u a t i o n a p r o c e d u r e has been d e v e l o p e d that allows the diff r a c t i o n i n f o r m a t i o n (selected area diffraction, m i c r o - d i f f r a c t i o n ) to be o b t a i n e d o n - l i n e f o l l o w i n g t r a n s f e r of data from the column to a computer. The m i c r o s c o p e p r o v i d e s for an i n t e r n a l diff r a c t i o n standard. The c o n n e c t i o n between the column and the c o m p u t e r is p e r f o r m e d by: a) a h y b r i d s c a n n i n g m o d u l e w h i c h integrates s c a n n i n g t e c h n i q u e s w i t h TEM o p e r a t i o n modes. This m o d u l e fits into the STEM s y s t e m and in one of the m o d e s the m i c r o d i f f r a c t i o n p a t t e r n is s c a n n e d across the STEM detector. In this w a y the d i f f r a c t i o n p a t t e r n is s e q u e n t i a l l y a v a i l a b l e in time and ready as c o m p u t e r input data
Abstracts of 34th Scandinavian Society Annual Meeting w h i c h is p a s s e d through: b) a S T E M - c o m p u t e r interface to the computer. The interplanar angles and zone axis can be derived from the r e f l e c t i o n coordinates. The d-values are o b t a i n a b l e by using the internal d i f f r a c t i o n s t a n d a r d for calibration. The EDX/EELS s y s t e m coupled with the S T E M - c o m p u t e r interface allows all data to be c o l l e c t e d in one place and to be c o r r e l a t e d to p r o v i d e the user w i t h i n f o r m a t i o n of high reliability.
413
ticular i m p o r t a n c e in m i c r o s t r u c t u r a l d e v e l o p m e n t is the fcc/hcp phase transformation w h i c h occurs in Co base alloys. O r d e r e d phases b a s e d on the fcc and hcp crystal structures have been observed. The p a r t i c u l a r m o r p h o l o g y of these precipitates depends upon the way in w h i c h the t r a n s f o r m a t i o n is carried out (e.q. q u e n c h i n g and tempering, or direct isothermal transformation). Both continuous and d i s c o n t i n u o u s types of p r e c i p i tation have been observed. F u r t h e r work has c o m m e n c e d on the p o s s i b i l i t y of similar t r a n s f o r m a t i o n s o c c u r r i n g in C o - N i - W - C alloys.
A P P L I C A T I O N S OF A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y IN A L L O Y STEEL R E S E A R C H P R O P E R T I E S OF T I T A N I U M CARBIDE G. L. Dunlop, L.-E. T. T h o r v a l d s s o n
S v e n s s o n and
D e p a r t m e n t of Physics, v e r s i t y of Technology, Sweden
Else Breval C h a l m e r s Uni412 96 G~teborg,
A 200 kV T Z M / S T E M i n s t r u m e n t e q u i p p e d w i t h q u a n t i t a t i v e EDS facilities has been used in r e s e a r c h on m i c r o s t r u c t u r a l d e v e l o p m e n t in alloy steels. Two particular alloy types have been s t u d i e d in depth: p o w d e r m e t a l l u r g i c a l high speed steels, and s t a b i l i z e d a u s t e n i t i c stainless steels. The c o m p o s i t i o n s of large carbide p r e c i p i t a t e s (e.g. p r i m a r y carbides in high speed steel) can readily be d e t e r m i n e d by STEM/EDS of thin foils w h i l e for smaller p r e c i p i t a t e s the carbon e x t r a c t i o n replica t e c h n i q u e is used. P a r a l l e l work has also made use of atomprobe field-ion m i c r o s c o p y to analyze very fine p r e c i p i t a t e d i s p e r s i o n s in these materials. Solute c o n c e n t r a t i o n p r o f i l e s have also been d e t e r m i n e d by STEM/EDS of thin foils w i t h c o n n e c t i o n s for the effects of b e a m s p r e a d i n g . Of p a r t i c u l a r i n t e r e s t is the formation and h e a l i n g of C r - d e p l e t e d zones in the vicinity of grain b o u n d a r i e s in a u s t e n i t i c stainless s£eels.
A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y OF PHASE T R A N S F O R M A T I O N S IN Co-W-C ALLOYS G. W i r m a r k and G. L. D u n l o p D e p a r t m e n t of Physics, v e r s i t y of T e c h n o l o g y , Sweden
C h a l m e r s Uni412 96 Goteborg,
The b i n d e r p h a s e of c e m e n t e d carbide tool m a t e r i a l s is g e n e r a l l y a C o - W - C alloy. A n u m b e r of alloys in this system have b e e n i n v e s t i g a t e d w i t h r e s p e c t to the m i c r o s t r u c t u r e s w h i c h can be d e v e l o p e d by h e a t treatment. Use has been made of T E M / S T E M w i t h EDS. Of par-
L a b o r a t o r y of A p p l i e d P h y s i c s I, Technical U n i v e r s i t y of Denmark, B u i l d i n g 307, D K - 2 8 0 0 Lyngby, D e n m a r k
T i t a n i u m carbide is used in the machining industry as a 5 ~m thin coating of p o l y c r y s t a l l i n e TiC on the cutting tool in order to improve its w e a r properties. To reveal the b e h a v i o u r of the TiC coating on hard metal cutting tools a b a s i c study of the p r o p e r t i e s of s i n g l e - c r y s t a l TiC and TiC p o w d e r has been carried out. As m a t e r i a l s TIC0.99 , TIC0.79 and TIC0.64 are used. This study comprises two properties: i) the r e s p o n s e of TiC x to stress, 2) the o x i d a t i o n of TIC0.99 at 700oc to 900°C w i t h d i f f e r e n t p a r t i a l p r e s s u r e of 02 . The i n f l u e n c e of stress at r o o m temp e r a t u r e leads either to cracks ({i00} cleavage or c h o n c h o i d a l fracture) or to p l a s t i c d e f o r m a t i o n ({iii}, {ii0} and {i00} ). The h a r d n e s s and the a n i s o t r o p y of TiC x d e c r e a s e w i t h d e c r e a s e d x but are d e p e n d e n t on the g e o m e t r y of the d i a m o n d i n d e n t e r and the load. By h e a t i n g of TIC0.99 p o w d e r b e t w e e n 700oc and 900oc at a p a r t i a l p r e s s u r e of oxygen of about 10 -3 Pa the o x i d a t i o n p r o d u c t Ti203 is formed. The c r y s t a l l o graphic o r i e n t a t i o n of the TiC and the Ti203 e s t a b l i s h e d by e l e c t r o n d i f f r a c t i o n t e c h n i q u e s is:
[n0]T±C II [222]TiC H [13i]TiC 11
[3030]Ti203 [~4~0]Ti203 [2240]Ti203
By h e a t i n g of TIC0.99 b e t w e e n 700°C and 900oc at a p a r t i a l p r e s s u r e of o x y g e n of about 2-10 ~ Pa the o x i d a t i o n Product TiO 2 is formed. Both rutile and anatase have been detected.
Abstracts of 34th Scandinavian Society Annual Meet#Tg
414
A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y OF Si3N 4BASED HIGH T E M P E R A T U R E C E R A M I C S
was s u r p r i s i n g l y constant, greater for C r - d i s p e r s o i d s Mn-dispersoids.
and was than for
L. Falk, P. Nilsson and G. L. Dunlop D e p a r t m e n t of Physics, versity of Technology, Sweden
C h a l m e r s Uni412 96 Goteborg,
The high temperature m e c h a n i c a l properties of ceramic m a t e r i a l s are highly sensitive to microstructure. For example the p r e s e n c e of thin i n t e r g r a n u l a r glass films p r o m o t e s grain b o u n d a r y sliding and c a v i t a t i o n and thus weakens the material. In the present i n v e s t i g a t i o n the m i c r o s t r u c t u r e of p r e s s u r e l e s s sintered and hot i s o s t a t i c p r e s s e d Si3N 4 and SiAION has been i n v e s t i g a t e d by T E M / S T E M w i t h EDS special specimen p r e p a r a t i o n techniques n e c e s s a r y for t r a n s m i s s i o n microscopy. P a r t i c u l a r a t t e n t i o n is paid to the p r e s e n c e and composition of glass phases r e s u l t i n g from the s i n t e r i n g processes. This enables a c o m p a r i s o n of s i n t e r i n g techniques to be made.
C O M P A R I S O N OF QUENCH S E N S I T I V I T Y IN A L - M G - S I ALLOYS C O N T A I N I N G MN OR CR A. L. Dons and OL Lohne SINTEF, Dept. of M e t a l l u r g y , T r o n d h e i m - N T H , Norway
M I C R O F R A C T O G R A P H Y OF O F F - S H O R E CONSTRUCTIONS J. Hjelen, A. L. Dons and T. H. Johansen* SINTEF, Dept. of M e t a l l u r g y , 7034 T r o n d h e i m - N T H , Norway; * M e t a l l u r g i c a l Institute, NTH, 7034 T r o n d h e i m - N T H , Norway
A f t e r a tragic p l a t f o r m accident in the North Sea, the fracture was investigated by SINTEF and NTH. The fractured p l a t f o r m part had been lying in the sea for more than a month after the accident, and the first task was to remove a coating of lime and rust w i t h o u t d a m a g i n g any part of the surface underneath. Having m a n a g e d to clean some areas, we o b s e r v e d a v a r i e t y of fracture features. In a d d i t i o n to fatigue fracture with striations, ductile fracture, brittle fracture w i t h river p a t t e r n s and i n t e r c r y s t a l l i n e fracture were observed. Examples of c l e a n i n g methods and f r a c t o g r a p h i c details are given.
7034
In AIMgSi alloys q u e n c h e d from about 500oc, the u l t i m a t e h a r d n e s s after aging depends to some extent upon the quench rate. Slow cooling will give 8'-Mg2Sirods time to nucleate, and as they bind Mg and Si, there w i l l be less of these elements available to form h a r d e n i n g p r e c i p i t a t e s during the aging process. A d d i t i o n of Mn or Cr leads to formation of dispersoids, w h i c h act as n u c l e a t i o n centers for 8'-Mg2Si-rods, so that Mn- or C r - a d d i t i o n to the alloy makes fast q u e n c h i n g even more important. In the p r e s e n t work, we have c o m p a r e d the influence of 0.56% Mn to that of 0.23% Cr in an A I - 0 . 6 % M g - l . 0 % S i - a l l o y . The alloys w e r e h o m o g e n i z e d at different temperatures, q u e n c h e d in w a t e r or cooled in air, aged to m a x i m u m hardness, and then the hardness, tensile strength and y i e l d strength were measured. Thin foils w e r e p r e p a r e d and s t u d i e d in TEM at d i f f e r e n t stages in the process. As expected, d i s p e r s o i d s containing Mn and Cr w e r e observed, and aircooled specimens c o n t a i n e d 8'-Mg2Si-rods. For a i r - c o o l e d alloys h o m o g e n i z e d at 520oc an i n t e r e s t i n g effect was observed. E y e n if the amount of dispersoids v a r i e d by m o r e than a factor 2 w i t h i n the same thin foil, the n u m b e r of 8'-Mg2Si-rods
Q U A N T I T A T I V E STEM-EDS A N A L Y S E S OF THIN WIRE SPECIMENS H.-O Andr~n, M. Hellsing, and H. Nord~n D e p a r t m e n t of Physics, v e r s i t y of T e c h n o l o g y , Sweden
A. H e n j e r e d
C h a l m e r s Uni412 96 Goteborg,
In a S T E M - b a s e d m i c r o a n a l y t i c a l system the lateral r e s o l u t i o n is limited to 10-20 nm by b e a m s p r e a d i n g and the depth r e s o l u t i o n is d e t e r m i n e d by the p e n e t r a t i o n depth of the electrons. This leads to an a v e r a g i n g over not too well d e f i n e d volumes w h e n p e r f o r m i n g analyses w i t h high spatial resolution. It has t h e r e f o r e been found useful to compare the results from this t e c h n i q u e w i t h those from another m i c r o a n a l y t i c a l technique, a t o m - p r o b e m i c r o a n a l y s i s , w h e r e signal g e n e r a t i o n and d e t e c t i o n relies upon other p h y s i c a l principles. Both lateral r e s o l u t i o n and depth r e s o l u t i o n of the atom probe is about 1 nm and the r e l a t i v e s e n s i t i v i t y for d i f f e r e n t atomic species seems to be c o n s t a n t and i n d e p e n d e n t of s p e c i m e n composition. The use of a t o m - p r o b e specimens, s h a p e d as thin tips, in STEM EDX analysis has the added a d v a n t a g e that local s p e c i m e n thickness, depth and size of s p e c i f i c
Abstracts of 34 th Scandinavian Society Annual Meeting
f e a t u r e s a n d t h i c k n e s s of s u r f a c e l a y e r (if p r e s e n t ) c a n b e m e a s u r e d d i r e c t l y .
HIGH
RESOLUTION ELECTRON MICROSCOPY IN M A T E R I A L S S C I E N C E
T H E S T U D Y O F O R D E R E D A L L O Y S BY M E A N S HIGH RESOLUTION ELECTRON MICROSCOPY AND ELECTRON DIFFRACTION* G. v a n T e n d e l o o , S. A m e l i n c k x * *
J.
van Landuyt
OF
and
Laboratorium voor Hoogspanningselektronenmikroskopie, Rijksuniversitair Centrum, B 2020 - Antwerpen, Belgium; * * A l s o at S . C . K . , B - 2 4 0 0 - M o l , Belgium
The instrumental resolution of presentday electron microscopes allows obtaining of atomic resolution under favourable circumstances. The combination of high resolution electron microscopic imaging and selected area electron diffraction h a s p r o v e d to be o f g r e a t h e l p in e l u c i d a t i n g the s t r u c t u r e s o f c r y s t a l s w h i c h are h i g h l y f r a g m e n t e d in s y m m e t r y - r e l a t e d d o m a i n s , s u c h as o r d e r e d a l l o y s . The use of the superlattice reflections either in the d a r k f i e l d o r in t h e b r i g h t f i e l d mode allows revelation preferentially of the c o n f i g u r a t i o n s o f l i g h t m i n o r i t y a t o m s in g o l d m a n g a n e s e a n d g o l d magnesium alloys. In o u r c o n t r i b u t i o n w e d i s c u s s s o m e r e c e n t r e s u l t s o n the i d e n t i f i c a t i o n a n d the s t u d y o f n e w p h a s e s in the A u - M n I a n d the A u - M g 2 s y s t e m s u s i n g t h e d e s c r i b e d techniques. It is s h o w n t h a t s e v e r a l different long period structures may occ u r s i m u l t a n e o u s l y i n the s a m e s p e c i m e n . Very small composition differences apparently induce different structures, the d i f f e r e n c e s in c o m p o s i t i o n b e i n g i n c o r porated along non-conservative anti-phase boundaries. S o m e r e s u l t s o b t a i n e d in t h e s t u d y o f o t h e r a l l o y s a r e d i s c u s s e d b r i e f l y also. R e f e r e n c e s for A u - M n s y s t e m : G. v a n T e n d e l o o , R. w o l f , S. A m e l i n c k x , Phys. Stat. Sol. (a) 40 (1977) 531. G. v a n T e n d e l o o , R. W o l f , D. v a n Dyck, S. A m e l i n c k x , Phys. Stat. Sol. (a) 47 (1978) 105. R. Wolf, G. v a n T e n d e l o o , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. Stat. Sol. (a] 47 (1978) 241. G. v a n T e n d e l o o , R. W o l f , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. S t a t . Sol. (a) 47 (1978) 539. G. v a n T e n d e l o o , S. A m e l i n c k x , Phys. Stat. Sol. (a) 47 (1978) 555. R. W o l f , G. v a n T e n d e l o o , J. v a n L a n d u y t , S. A m e l i n c k x , P h y s . Stat. Sol. (a) 48 (1978) 39.
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G. v a n T e n d e l o o and S. A m e l i n c k x , Phys. Stat. Sol. (a) 49 (1978) 337. G. v a n T e n d e l o o , R. de R i d d e r , S. A m e l i n c k x , Phys. Star. Sol. (a) 49 (1978) 655. G. v a n T e n d e l o o and S. A m e l i n c k x , Phys. Stat. Sol. (a) 51 (1979) 141. G. v a n T e n d e l o o , M. v a n Sande, S. A m e l i n c k x , Phys. Star. Sol. (a) 55 (1979) 681. G. v a n T e n d e l o o , J. v a n L a n d u y t , S. Amelinckx, "Electron Microscopy 1980" ed. P. B r e d e r o o and G. B o o m (7th Eur. Congr. on E l e c t r o n M i c r o s c o p y F o u n d a tion, L e i d e n , 1980) vol. i, p. 226. G. v a n T e n d e l o o , R. W o l f , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. Star. Sol. (a) 60 (1980) 581. R e f e r e n c e s for A u - M g s y s t e m : M. v a n Sande, G. v a n T e n d e l o o , S. A m e l i n c k x , P. Airo, Phys. Stat. Sol. (a) 55 (1979) 681. G. v a n T e n d e l o o , M. v a n Sande, S. A m e l i n c k x , P. Airo, " E l e c t r o n M i c r o s c o p y 1980" ed. P. B r e d e r o o and G. B o o m (7th Eur. C o n g r . on E l e c t r o n M i c r o s c o p y F o u n d a t i o n , L e i d e n , 1980) vol. l, p. 276.
THE CRYSTAL STRUCTURE OF SOME NEW ANTIGORITE MODIFICATIONS A.
Olsen Institute of Physics, O s l o , P. O. B o x 1 0 4 8 ,
University of O s l o 3, N o r w a y
A n t i g o r i t e is a s e r p e n t i n e m i n e r a l with an alternating wave structure. The r e p e a t o f t h e c o r r u g a t i o n is a l o n g t h e A - a x i s w h i c h c a n v a r y f r o m 17 R t o ll0 ~. A n t i g o r i t e is k n o w n t o h a v e a o n e ' l a y e r s t r u c t u r e w i t h C ~ 7.3 ~ a n d B ~ 9 . 3 R. The present paper reports several new modifications of antigorite with 10-1ayer structures. These minerals have been identified by a combination of transmission electron microscopy and diffraction, X-ray powder diffraction and X-ray microanalysis. The distance between the reflections in the A*-direction corresp o n d s t o a s u p e r p e r i o d a b o u t 38 ~ . T h e structure of a 10-1ayer antigorite with c e l l p a r a m e t e r s : A = 3 8 . 1 0 R; B = 9 . 2 4 6 R a n d C = 7 2 . 6 0 ~; ~ 8 = 7 = 90 ° h a s b e e n s t u d i e d in d e t a i l . The number of atoms in t h e u n i t c e l l is a b o u t 2 5 5 0 , a n d ~ e composition can be described by th e formula: (Sgl_x_yFexAly)420 (Sil_zAlz)300 O780+420y~300~ (OH)540-420y+300z w h e r e x < 0.i; 6 < 0 . 0 7 £ z < 0.0~3. By comparing calculated electron 4iffraction
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Abstracts of 34th Scandinavian Society Annual Meeting
patterns from different models with exp e r i m e n t a l patterns, the most probable, ideal structure has been determined. The principles controlling this structure can easily be applied to explain the exist e n c e of the other similar antigorites o b s e r v e d in nature. The main d i f f e r e n c e between these structures is the p o s i t i o n of 4- and 8-membered Si205 rings. SYMMETRY AND S T R U C T U R E D E T E R M I N A T I O N OF B a - N d - T i - O X I D E S BY C O M B I N I N G CBED AND HREM A. Olsen*, R. S. Roth** and P. Goodman*** * I n s t i t u t e of P h y s i c s , U n i v e r s i t y of Oslo, P. O. B o x 1048, O s l o 3, N o r w a y ; * * N a t i o n a l B u r e a u of S t a n d a r d s , W a s h i n g t o n , D.C. 2 0 2 3 4 , U . S . A . ; a n d * * * C S I R O , D i v i s i o n o f C h e m i c a l Physics, P. O. B o x 160, C l a y t o n , V i c t o r i a , A u s t r a l i a 3168.
High resolution lattice imaging ( H R ~ ) is a p o w e r f u l tool to investigate crystal structures in complex oxide systems. Such images can frequently be used on their own to d e t e r m i n e crystal symmetry) this is only o c c a s i o n a l l y p o s s i b l e w h e n a short unit cell axis is parallel to the incident beam. One of the w e a k n e s s e s in this m e t h o d is that asymmetries may be i n t r o d u c e d into the image by asymmetries in the i l l u m i n a t i o n (i.e. a d i s p l a c e d objective aperture) or to i n c o r r e c t or inaccurate crystal alignment. On the other hand, c o n v e r g e n t b e a m d i f f r a c t i o n is an e s t a b l i s h e d means of d e t e r m i n i n g crystal symmetry, free from the above shortcomings, but usually suffers from the weaknesses: (a) the area i l l u m i n a t e d is very large c o m p a r e d w i t h a unit cell and so the data provide@ an average symmetry, and (b) w e a k superstructure reflections are frequently not visible in the CBED pattern. By c o m b i n i n g HREM and CBED many of these w e a k n e s s e s of the individual techniques can be o v e r c o m e or become irrelevant. This has been p a r t i c u l a r l y true in the p r e s e n t study about s y m m e t r y elements, space group and structure of some Ba-Nd-Ti-oxides.
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y D I S L O C A T I O N S AND INTERFACES IN SEMICONDUCTORS
OF
A. Olsen* and J. C. H. Spence** *Institute of Physics, University of o s l o , P. 0. B o x 1 0 4 8 , O s l o 3, N o r w a y ; **Department of Physics, Arizona State U n i v e r s i t y , Tempe, AZ 8 5 2 8 1 , U S A
Structure imaging by high r e s o l u t i o n t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y has given s o l i d - s t a t e chemists and m i n e r a l ogists new insight into many defect structures and phase t r a n s f o r m a t i o n mechanisms in recent years. In the field of s e m i c o n d u c t o r physics, however, there have been few really useful results from this technique. This is chiefly because it is not p r e s e n t l y p o s s i b l e to obtain a s t r u c t u r e image at atomic resolution of any common semiconductor. Here a structure image is defined as a lattice image w h i c h faithfully reveals a crystal's structure to some limited resolution and w h i c h was r e c o r d e d under i n s t r u m e n t a l conditions w h i c h are independent of the structure. Since the information r e s o l u t i o n limit set by electronic i n s t a b i l i t i e s is far below the point r e s o l u t i o n of a m o d e r n t r a n s m i s s i o n microscope, it is p o s s i b l e to obtain, by choice of focus and thickness, clear lattice images both r e s e m b l i n g and not r e s e m b l i n g the true crystal structure. The p r e s e n t paper reports a study of the core structure of d i s l o c a t i o n s in Si and c o m p o s i t i o n a l analysis across interfaces in III-V semiconductors. All the details in the e x p e r i m e n t a l images o b t a i n e d in a JEOL 100B m i c r o s c o p e lie b e y o n d the c o n v e n t i o n a l point r e s o l u t i o n limit. The main part of the paper is concerned w i t h i n t e r p r e t a t i o n of such image details.
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y STUDIES IN THE T U N G S T E N O X Y G E N SYSTEM W u b e s h e t Sahle and M a r g a r e t a S u n d b e r g Department of Inorganic Chemistry, Arrhenius Laboratory, University of Stockholm, S - 1 0 6 91 S t o c k h o l m , Sweden
High r e s o l u t i o n e l e c t r o n m i c r o s c o p y (HREM) technique has b e e n used to characterize d i f f e r e n t phases in the region W02.72 - WO3. 0 of the t u n g s t e n - o x y g e n system. The o r d e r e d and defect structures of the phases w e r e d e t e r m i n e d by means of e l e c t r o n d i f f r a c t i o n p a t t e r n s and from HREM images of thin crystal fragments (thickness < 100 ~). The resolution in the images was ~ 3.5 R. The e l e c t r o n d i f f r a c t i o n p a t t e r n of a crystal gave i n f o r m a t i o n about the average crystal structure, w h i l e the H R E M images gave d e t a i l e d i n f o r m a t i o n about the local crystal s t r u c t u r e of the fragments. The f o l l o w i n g phases w e r e found: {102} c r y s t a l l o g r a p h i c shear (CS) structures (W0~2.93 - WO~3.0) , {103}CS-structures (WO%2.88 - W0~2.93) , and the W2~068 (WO~2.83~ and the W 1 8 0 4 q (WO 2 72 ) structure types . All these s £ r u c t u r e s
Abstracts of 34th Scandinavian Society Annual Meeting are b u i l t up of d i f f e r e n t rather complicated s t r u c t u r e units, and will be exemp l i f i e d by HREM images and s t r u c t u r e models. In the C S - s t r u c t u r e types, twinning, d i s o r d e r and f a u l t i n g in the C S - p l a n e s were f r e q u e n t l y observed. Defects and t w i n n i n g were also found in the W 2 4 0 6 8 - p h a s e , w h i l e W18049 a p p e a r e d to be very well o r d e r e d (with a few exceptions). I n t e r g r o w t h b e t w e e n the various phases has been observed. E x a m p l e s of d i f f e r e n t types of defects and i n t e r g r o w t h are presented. Since defects and t w i n n i n g are freq u e n t l y o c c u r r i n g in this system, the HREM technique has p r o v e d to be an i n v a l u a b l e tool, as a c o m p l e m e n t or substitute to the c l a s s i c a l X - r a y single crystal studies. The W 2 4 0 6 8 structure, of a new type, has i n d e e d been d e t e r m i n e d d i r e c t l y from HREM imagesl since crystals suitable for X - r a y d i f f r a c t i o n w o r k w e r e not a v a i l a b l e 2. i. 2.
s. Berglund and W. J. Sahle, State Ch~m. 36 (1981) 66-73. M. Sundberg, Chemica Scripta (1978-79) 161-66.
Solid 14
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y A P P L I E D TO T U N G S T E N B R O N Z E S AND ANALOGOUS COMPOUNDS Lars Kihlborg, Sharma
Altaf
Hussain*
and Renu
D e p a r t m e n t of I n o r g a n i c Chemistry, A r r h e n i u s Laboratory, U n i v e r s i t y of Stockholm, S-I06 91 Stockholm, Sweden; *permanent address University of Dacca, B a n g l a d e s h T u n g s t e n b r o n z e s is the name of a group of oxides w i t h the general formula AxWO3, 0 < x < i. In the m o s t typical systems A is an alkali metal. W i t h i n the c o m p o s i t i o n region d i f f e r e n t phases form d e p e n d i n g on x and the size of A. These phases g e n e r a l l y have w i d e h o m o g e n e i t y ranges in x ahd are thus typical n o n s t o i c h i o m e t r i c compounds. They are c h e m i c a l l y very inert and some p o s s e s s very intere s t i n g p h y s i c a l p r o p e r t i e s , .such as high m e t a l l i c conductivity. The t u n g s t e n b r o n z e s are very w e l l s u i t e d for s t r u c t u r e i m a g i n g in an electron m i c r o s c o p e w i t h a b o u t 3.5 ~ resolution. H R E M studies have r e v e a l e d an e x t e n s i v e family of p h a s e s forming w i t h A = K, Rb and Cs for low values of x. These have b e e n n a m e d i n t e r g r o w t h tungsten b r o n z e s (ITB) since £heir structures, as r e v e a l e d by HREM images, can be cons i d e r e d as i n t e r g r o w t h on a unit cell level of WO 3 and one of the o t h e r tungsten bronzes, d e s i g n a t e d HTB (hexagonal
417
tungsten bronze). The p r o p o r t i o n of the two s t r u c t u r e elements can vary, w h e r e b y d i f f e r e n t m e m b e r s of this s t r u c t u r e family are formed. Disorder, long-periodic m o d u l a t i o n and various types of defects have also been o b s e r v e d in the images. Recent studies of fully o x i d i z e d analogues, in w h i c h part of the t u n g s t e n has been r e p l a c e d by a p e n t a v a l e n t m e t a l (V, Nb or Ta) have e x t e n d e d the n u m b e r of k n o w n m e m b e r s of the ITB family cons i d e r a b l y and also r e v e a l e d s t r u c t u r e s r e p r e s e n t i n g the extreme ends of this i n t e r g r o w t h range: WO 3 w i t h i s o l a t e d slabs of HTB and vice versa. V e r y comp l i c a t e d i n t e r g r o w t h s e q u e n c e s have also been observed, the o r i g i n of w h i c h is an i n t r i g u i n g question. This s y s t e m thus is an i l l u s t r a t i o n of the great u s e f u l n e s s of the HREM technique in solid state chemistry. The imp o r t a n c e of the m e t h o d w i l l i n e v i t a b l y grow still further as the r e s o l u t i o n of c o m m e r c i a l m i c r o s c o p e s i n c r e a s e s and even d e n s e l y p a c k e d s t r u c t u r e s can be imaged.
Selected Abstracts from the
T h i r t y - f o u r t h Annual M e e t i n g of The S c a n d i n a v i a n Society for E l e c t r o n M i c r o s c o p y
SCANDEM-81
D e p a r t m e n t of P a t h o l o g y Huddinge Hospital Stockholm 3-5 June 1981
The S c a n d i n a v i a n Society for E l e c t r o n M i c r o s c o p y h e l d its 34th annual meeting, SCANDEM-81, in S t o c k h o l m on 3-5 June 1981. F r o m over 290 participants, the o r g a n i z e r s have s e l e c t e d a number of abstracts concerning m a t e r i a l s science w h i c h should be of i n t e r e s t to U ! t r a m i c r o s c o p y ' s readers. (The b i o l o g i c a l aspects of the S C A N D E M - 8 1 p r o g r a m w i l l appear later in J o u r n a l of U l t r a s t r u c t u r e Research.)
Bj~rn V. J o h a n s e n
0304-3991/81/0000-0000/$02.50 © 1981 North-Holland
Abstracts of 34th Scandinavian SocieO; Annual Meet#zg E L E C T R O N M I C R O S C O P Y IN MATERIALS SCIENCE
5. 6.
A P P L I C A T I O N OF E L E C T R O N M I C R O S C O P Y IN THE STUDY OF P O L Y M E R C R Y S T A L L I Z A T I O N AND IN THE QUEST OF A C H I E V E M E N T OF DESIRABLE PROPERTIES A.
Keller H. H. W i l l s P h y s i c s L a b o r a t o r y , U n i v e r s i t y o f B r i s t o l , R o y a l Fort, T y n d a l l A v e n u e , B r i s t o l BS8 ITL, U.K.
The e m p h a s i s of the lecture is twofold. F i r s t it is to d e m o n s t r a t e the p o w e r of p r i m a r y real space imaging in the much d i s p u t e d area of how l o n g - c h a i n po l y m e r s o r g a n i z e t h e m s e l v e s to form crystals, with due e v a l u a t i o n of all p r i n c i p a l e v i d e n c e and of the t e c h n i c a l ities i n v o l v e d (on the much d i s p u t e d problem of how r e g u l a r l y and a d j a c e n t l y the chains fold up along the g r o w i n g crystal face as o p p o s e d to m e r e l y 'freezing in' from the r a n d o m state, see ref. i). Secondly, it will be d e m o n s t r a t e d on a few s e l e c t e d e x a m p l e s of how the study of e l e c t r o n m i c r o s c o p i c m o r p h o l o g y , w h e n applied at the right stage, in the right c o m b i n a t i o n w i t h o t h e r techniques, can d e c i s i v e l y further the a c h i e v e m e n t of high m o d u l u s and high strength, w h i c h is i n t r i n s i c to the v a l e n c e b o n d e d long chain molecule, but n o t usually a c h i e v e d in c o n v e n t i o n a l t e c h n o l o g i c a l practice. In this latter r e s p e c t fibrous c r y s t a l l i zation in p r e o r i e n t e d s o l u t i o n s and melts leading to the s o - c a l l e d 'shish-kebabs' and 'row structures' w i l l be d i s c u s s e d 2-~ t o g e t h e r w i t h a p a r t i c u l a r e x a m p l e of 'morphological engineering' w h e r e a predominantly platelet-containing structure a p p r o p r i a t e l y i n i t i a t e d by fibres has a p a r t i c u l a r l y b e n e f i c i a l e f f e c t on promoting s t i f f n e s s 5. The last case also provides an e x p l a n a t i o n in m o r p h o l o g i c a l terms of why and how certain o r i e n t e d p o l y m e r s may improve their s t i f f n e s s on storage6, 7 .It is h o p e d that the latter examples, b e s i d e s b e i n g i n s t r u c t i v e for the e l e c t r o n m i c r o s c o p y of polymers, may also o f f e r some t e c h n o l o g i c a l g u i d e l i n e s in the a c h i e v e m e n t and p r o d u c t i o n of o r i e n t e d fibres and films w i t h advantageous properties. I. 2. 3.
4.
Faraday Discussion No. 68 (1979), see Introduction by A. Keller, p. 145. A. Keller, J. Polymer Sci. Polymer Symposia 58 (1977) 395. A. Keller, in Ultra-high modulus polymers (ed. A. Cifferi and I. M. Ward), Appl. Sci. Publishers, 1979. A. Keller and P. J. Barham, Plastics and Rubber International 6 (1981) 19.
7.
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J. A. Odell, D. T. Grubb and A. Keller, Polymer 19 (1978) 617. R. G. C. Arridge, P. J. Barham and A. Keller, J. Polymer Sci. Polymer Phys. ed. 15 (1977) 389. J. A. Odell, A. Keller and M. Miles, to be published.
THE T R A N S M I S S I O N E L E C T R O N A CHEMICAL LABORATORY
MICROSCOPE
AS
K. E. E a s t e r l i n g D e p a r t m e n t of E n g i n e e r i n g M a t e r i a l s , U n i v e r s i a of L u l e ~ , S w e d e n
The most i m p o r t a n t d e v e l o p m e n t in e l e c t r o n m i c r o s c o p y in recent years has u n d o u b t e d l y been the i n t r o d u c t i o n of c o m b i n e d T E M / S T E M systems. This c o m b i n a t i o n allows us to retain all the a d v a n t a g e s of high r e s o l u t i o n m i c r o s c o p y of c o n v e n t i o n a l t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y t o g e t h e r w i t h the p o s s i b i l i t i e s of u s i n g the i n s t r u m e n t as a high r e s o l u t i o n e l e c t r o n m i c r o probe. In addition, the d i g i t i z e d image of the S T E M / S E M TV d i s p l a y can be u t i l i z e d for p a r t i c l e analysis w o r k or i n c o n j u n c t i o n w i t h in-situ d e f o r m a t i o n experiments. In o t h e r words, w i t h i n the the one system, most of the facilities of a c h e m i c a l / m a t e r i a l s testing laboratory are available. E x a m p l e s of how such a s o p h i s t i c a t e d s y s t e m c o n t a i n i n g (TEM-STEM-PASTEM-EDX-EELS-in-situ d e f o r m a t i o n stage), etc. can be used to help solve m a t e r i a l s p r o b l e m s are shown in the talk.
MATERIAL Lars-Eric
ANALYSIS
WITH
PIXE
Carlsson
Dept. o f N u c l e a r P h y s i c s , L u n d I n s t i tute o f T e c h n o l o g y , S o l v e g a t . 14, S - 2 2 3 62 Lund, S w e d e n
Method: In P I X E - a n a l y s i s (ParticleI n d u c e d X - r a y Emission) samples are i r r a d i a t e d w i t h p r o t o n s or h e a v i e r ions a c c e l e r a t e d in a p o t e n t i a l of 1-5 MV. The i n d u c e d X - r a y s are d e t e c t e d in an e n e r g y - d i s p e r s i v e s o l i d state detector. The m e t h o d is u s u a l l y a p p l i e d to e i t h e r thin or thick samples (< 1 m g / c m 2 and < 15 m g / c m 2 r e s p e c t i v e l y ) . The X - r a y b a c k g r o u n d in P I X E - a n a l y s i s is 3 to 4 o r d e r s of m a g n i t u d e lower than in e l e c t r o n - i n d u c e d analysis and the d e t e c t i o n limits a t t a i n a b l e w i t h irradi a t i o n times of a few m i n u t e s lies in the 0.5 - 5 p p m region for m a n y e l e m e n t s X - r a y a n a l y s i s can be done for all
Abstracts of 34th Scandinavian SocieO, Annual Meeting
412
elements h e a v i e r ~han Mg and by simultaneous d e t e c t i o n of particles or gammarays from n u c l e a r reactions many lighter elements may also be analysed. By using an a u t o m a t i c sample changer and a p o w e r f u l c o m p u t e r code with simultaneous fitting of b a c k g r o u n d and all X-ray peaks for up to 35 elements it is p o s s i b l e to p e r f o r m rapid, low-cost analysis of a large n u m b e r of samples. Thick samples: The most common means of e x c i t a t i o n is to use protons in the 2-3 M e V range. When a n a l y s i n g thick samples this e x c i t a t i o n allows for the d e t e c t i o n of Li, B, F, Na, M g and A1 by d e t e c t i n g gamma-rays from n u c l e a r reactions. This is done s i m u l t a n e o u s l y with X - r a y analysis of all h e a v i e r elements. In this w a y p r a c t i c a l l y all m a t r i x elements are m e a s u r e d and accurate thick target c o r r e c t i o n s b a s e d on f u n d a m e n t a l p a r a m e t e r s can be performed. This technique is p r e s e n t l y b e i n g s u c c e s s f u l l y applied to the analysis of both geological and b i o l o g i c a l material. The irradiation area used in these b r o a d b e a m analyses is u s u a l l y b e t w e e n 5 and 50 m m 2. Microbeam: The P I X E - m e t h o d is also very useful in m i c r o a n a l y s i s . Beam-spot diameters b e l o w 100 ~m can be a c h i e v e d by simply c o l l i m a t i n g the p a r t i c l e beam. With both c o l l i m a t i o n and focusing, beamspot sizes b e t w e e n 1 - i0 ~m d i a m e t e r may be obtained. B e a m current l i m i t a t i o n s increase the d e t e c t i o n limits a p p r o x i m a t e l y a factor of 10 c o m p a r e d to b r o a d b e a m analysis. Lateral d i s t r i b u t i o n s of d i f f e r e n t e l e m e n t s can be a c h i e v e d by s c a n n i n g the sample w i t h s t e p - m o t o r s or by s c a n n i n g the p a r t i c l e b e a m w i t h an e l e c t r o s t a t i c or m a g n e t i c sweep system. The m i c r o b e a m setup in Lund is, in its p r e s e n t status, capable of p r o d u c i n g b e a m spots down to 15 ~m diameter.
INDUSTRIAL P.-E.
APPLICATIONS
OF AES
Nilsson-Jatko
ASEA
AB,
72183
Vaster~s,
Sweden
Scanning Auger electron spectroscopy has p r o v e d to be a v e r s a t i l e t e c h n i q u e for s o l v i n g a wide range of m a t e r i a l problems. The e x c e l l e n t depth r e s o l u t i o n and the high lateral r e s o l u t i o n in combination with the ability to detect all e l e m e n t s with z ~ 3 make it a s t r o n g analytical instrument. This w i l l be illustrated w i t h examples from d e v e l o p m e n t projects w h e r e the AES t e c h n i q u e has been app l i e d and from p r o d u c t i o n p r o b l e m s involving c o n t a m i n a t e d surfaces, i n s u f f i c i e n t a d h e s i o n and m a t e r i a l e m b r i t t l e m e n t . As an introduction, p r i n c i p l e s of AES and ins t r u m e n t p e r f o r m a n c e are b r i e f l y covered.
AN A P P R O A C H DIFFRACTION
TO C O M B I N E X-RAY, EELS AND M I C R O A N A L Y S I S IN TEM
P. H a g e m a n n N. V. P h i l i p s ' G l o e i l a m p e n f a b r i e k e n , S & I Electron Optics Applications Laboratory, B u i l d i n g T Q I I I - p , 5600 MD Eindhoven, The N e t h e r l a n d s .
The a n a l y t i c a l t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y utilises the t e c h n i q u e s of X-ray analysis, e l e c t r o n energy loss s p e c t r o s c o p y and e l e c t r o n d i f f r a c t i o n to c h a r a c t e r i s e and analyse m i c r o - a r e a s and c o m p l e m e n t the b a s i c image information. It is of i n t e r e s t to note that the problems of q u a n t i f i c a t i o n of the i n f o r m a t i o n a v a i l a b l e to the user has reached different levels for each of the above methods. X-ray analysis has made the most p r o g r e s s over the last decade because of e x t e n s i v e t e c h n o l o g i c a l and app l i c a t i o n s effort. E l e c t r o n e n e r g y loss s p e c t r o s c o p y is c u r r e n t l y p o s s i b l e w i t h good r e s o l u t i o n in compact s p e c t r o m e t e r s and may in the future attain status as a routine tool in e l e m e n t a l analysis and with approp r i a t e e l e c t r o n optics a v a i l a b l e in all modes (TEM, STEM, (micro-) d i f f r a c t i o n ) . The third m e t h o d mentioned, e l e c t r o n diffraction, has r e c e i v e d an e x t e n s i o n to its a p p l i c a t i o n range since the introduction of m i c r o d i f f r a c t i o n to routine TEM work. Data a c q u i s i t i o n and q u a n t i f i cation of the e l e c t r o n d i f f r a c t i o n , however, has r e c e i v e d little a t t e n t i o n to date. The p h o t o g r a p h i c e m u l s i o n is still c o n s i d e r e d the s t a n d a r d r e g i s t r a t i o n medium. The a t t e n d a n t tedious p r o c e s s i n g r e q u i r e d to o b t a i n d i f f r a c t i o n data from it is a c c e p t e d as normal. This attitude is in obvious c o n t r a d i c t i o n to the current p r o g r e s s in the a u t o m a t i o n and d e v e l o p m e n t of q u a n t i t a t i v e X - r a y diff r a c t i o n analysis p r o c e s s e s . To redress this s i t u a t i o n a p r o c e d u r e has been d e v e l o p e d that allows the diff r a c t i o n i n f o r m a t i o n (selected area diffraction, m i c r o - d i f f r a c t i o n ) to be o b t a i n e d o n - l i n e f o l l o w i n g t r a n s f e r of data from the column to a computer. The m i c r o s c o p e p r o v i d e s for an i n t e r n a l diff r a c t i o n standard. The c o n n e c t i o n between the column and the c o m p u t e r is p e r f o r m e d by: a) a h y b r i d s c a n n i n g m o d u l e w h i c h integrates s c a n n i n g t e c h n i q u e s w i t h TEM o p e r a t i o n modes. This m o d u l e fits into the STEM s y s t e m and in one of the m o d e s the m i c r o d i f f r a c t i o n p a t t e r n is s c a n n e d across the STEM detector. In this w a y the d i f f r a c t i o n p a t t e r n is s e q u e n t i a l l y a v a i l a b l e in time and ready as c o m p u t e r input data
Abstracts of 34th Scandinavian Society Annual Meeting w h i c h is p a s s e d through: b) a S T E M - c o m p u t e r interface to the computer. The interplanar angles and zone axis can be derived from the r e f l e c t i o n coordinates. The d-values are o b t a i n a b l e by using the internal d i f f r a c t i o n s t a n d a r d for calibration. The EDX/EELS s y s t e m coupled with the S T E M - c o m p u t e r interface allows all data to be c o l l e c t e d in one place and to be c o r r e l a t e d to p r o v i d e the user w i t h i n f o r m a t i o n of high reliability.
413
ticular i m p o r t a n c e in m i c r o s t r u c t u r a l d e v e l o p m e n t is the fcc/hcp phase transformation w h i c h occurs in Co base alloys. O r d e r e d phases b a s e d on the fcc and hcp crystal structures have been observed. The p a r t i c u l a r m o r p h o l o g y of these precipitates depends upon the way in w h i c h the t r a n s f o r m a t i o n is carried out (e.q. q u e n c h i n g and tempering, or direct isothermal transformation). Both continuous and d i s c o n t i n u o u s types of p r e c i p i tation have been observed. F u r t h e r work has c o m m e n c e d on the p o s s i b i l i t y of similar t r a n s f o r m a t i o n s o c c u r r i n g in C o - N i - W - C alloys.
A P P L I C A T I O N S OF A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y IN A L L O Y STEEL R E S E A R C H P R O P E R T I E S OF T I T A N I U M CARBIDE G. L. Dunlop, L.-E. T. T h o r v a l d s s o n
S v e n s s o n and
D e p a r t m e n t of Physics, v e r s i t y of Technology, Sweden
Else Breval C h a l m e r s Uni412 96 G~teborg,
A 200 kV T Z M / S T E M i n s t r u m e n t e q u i p p e d w i t h q u a n t i t a t i v e EDS facilities has been used in r e s e a r c h on m i c r o s t r u c t u r a l d e v e l o p m e n t in alloy steels. Two particular alloy types have been s t u d i e d in depth: p o w d e r m e t a l l u r g i c a l high speed steels, and s t a b i l i z e d a u s t e n i t i c stainless steels. The c o m p o s i t i o n s of large carbide p r e c i p i t a t e s (e.g. p r i m a r y carbides in high speed steel) can readily be d e t e r m i n e d by STEM/EDS of thin foils w h i l e for smaller p r e c i p i t a t e s the carbon e x t r a c t i o n replica t e c h n i q u e is used. P a r a l l e l work has also made use of atomprobe field-ion m i c r o s c o p y to analyze very fine p r e c i p i t a t e d i s p e r s i o n s in these materials. Solute c o n c e n t r a t i o n p r o f i l e s have also been d e t e r m i n e d by STEM/EDS of thin foils w i t h c o n n e c t i o n s for the effects of b e a m s p r e a d i n g . Of p a r t i c u l a r i n t e r e s t is the formation and h e a l i n g of C r - d e p l e t e d zones in the vicinity of grain b o u n d a r i e s in a u s t e n i t i c stainless s£eels.
A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y OF PHASE T R A N S F O R M A T I O N S IN Co-W-C ALLOYS G. W i r m a r k and G. L. D u n l o p D e p a r t m e n t of Physics, v e r s i t y of T e c h n o l o g y , Sweden
C h a l m e r s Uni412 96 Goteborg,
The b i n d e r p h a s e of c e m e n t e d carbide tool m a t e r i a l s is g e n e r a l l y a C o - W - C alloy. A n u m b e r of alloys in this system have b e e n i n v e s t i g a t e d w i t h r e s p e c t to the m i c r o s t r u c t u r e s w h i c h can be d e v e l o p e d by h e a t treatment. Use has been made of T E M / S T E M w i t h EDS. Of par-
L a b o r a t o r y of A p p l i e d P h y s i c s I, Technical U n i v e r s i t y of Denmark, B u i l d i n g 307, D K - 2 8 0 0 Lyngby, D e n m a r k
T i t a n i u m carbide is used in the machining industry as a 5 ~m thin coating of p o l y c r y s t a l l i n e TiC on the cutting tool in order to improve its w e a r properties. To reveal the b e h a v i o u r of the TiC coating on hard metal cutting tools a b a s i c study of the p r o p e r t i e s of s i n g l e - c r y s t a l TiC and TiC p o w d e r has been carried out. As m a t e r i a l s TIC0.99 , TIC0.79 and TIC0.64 are used. This study comprises two properties: i) the r e s p o n s e of TiC x to stress, 2) the o x i d a t i o n of TIC0.99 at 700oc to 900°C w i t h d i f f e r e n t p a r t i a l p r e s s u r e of 02 . The i n f l u e n c e of stress at r o o m temp e r a t u r e leads either to cracks ({i00} cleavage or c h o n c h o i d a l fracture) or to p l a s t i c d e f o r m a t i o n ({iii}
[n0]T±C II [222]TiC H [13i]TiC 11
[3030]Ti203 [~4~0]Ti203 [2240]Ti203
By h e a t i n g of TIC0.99 b e t w e e n 700°C and 900oc at a p a r t i a l p r e s s u r e of o x y g e n of about 2-10 ~ Pa the o x i d a t i o n Product TiO 2 is formed. Both rutile and anatase have been detected.
Abstracts of 34th Scandinavian Society Annual Meet#Tg
414
A N A L Y T I C A L E L E C T R O N M I C R O S C O P Y OF Si3N 4BASED HIGH T E M P E R A T U R E C E R A M I C S
was s u r p r i s i n g l y constant, greater for C r - d i s p e r s o i d s Mn-dispersoids.
and was than for
L. Falk, P. Nilsson and G. L. Dunlop D e p a r t m e n t of Physics, versity of Technology, Sweden
C h a l m e r s Uni412 96 Goteborg,
The high temperature m e c h a n i c a l properties of ceramic m a t e r i a l s are highly sensitive to microstructure. For example the p r e s e n c e of thin i n t e r g r a n u l a r glass films p r o m o t e s grain b o u n d a r y sliding and c a v i t a t i o n and thus weakens the material. In the present i n v e s t i g a t i o n the m i c r o s t r u c t u r e of p r e s s u r e l e s s sintered and hot i s o s t a t i c p r e s s e d Si3N 4 and SiAION has been i n v e s t i g a t e d by T E M / S T E M w i t h EDS special specimen p r e p a r a t i o n techniques n e c e s s a r y for t r a n s m i s s i o n microscopy. P a r t i c u l a r a t t e n t i o n is paid to the p r e s e n c e and composition of glass phases r e s u l t i n g from the s i n t e r i n g processes. This enables a c o m p a r i s o n of s i n t e r i n g techniques to be made.
C O M P A R I S O N OF QUENCH S E N S I T I V I T Y IN A L - M G - S I ALLOYS C O N T A I N I N G MN OR CR A. L. Dons and OL Lohne SINTEF, Dept. of M e t a l l u r g y , T r o n d h e i m - N T H , Norway
M I C R O F R A C T O G R A P H Y OF O F F - S H O R E CONSTRUCTIONS J. Hjelen, A. L. Dons and T. H. Johansen* SINTEF, Dept. of M e t a l l u r g y , 7034 T r o n d h e i m - N T H , Norway; * M e t a l l u r g i c a l Institute, NTH, 7034 T r o n d h e i m - N T H , Norway
A f t e r a tragic p l a t f o r m accident in the North Sea, the fracture was investigated by SINTEF and NTH. The fractured p l a t f o r m part had been lying in the sea for more than a month after the accident, and the first task was to remove a coating of lime and rust w i t h o u t d a m a g i n g any part of the surface underneath. Having m a n a g e d to clean some areas, we o b s e r v e d a v a r i e t y of fracture features. In a d d i t i o n to fatigue fracture with striations, ductile fracture, brittle fracture w i t h river p a t t e r n s and i n t e r c r y s t a l l i n e fracture were observed. Examples of c l e a n i n g methods and f r a c t o g r a p h i c details are given.
7034
In AIMgSi alloys q u e n c h e d from about 500oc, the u l t i m a t e h a r d n e s s after aging depends to some extent upon the quench rate. Slow cooling will give 8'-Mg2Sirods time to nucleate, and as they bind Mg and Si, there w i l l be less of these elements available to form h a r d e n i n g p r e c i p i t a t e s during the aging process. A d d i t i o n of Mn or Cr leads to formation of dispersoids, w h i c h act as n u c l e a t i o n centers for 8'-Mg2Si-rods, so that Mn- or C r - a d d i t i o n to the alloy makes fast q u e n c h i n g even more important. In the p r e s e n t work, we have c o m p a r e d the influence of 0.56% Mn to that of 0.23% Cr in an A I - 0 . 6 % M g - l . 0 % S i - a l l o y . The alloys w e r e h o m o g e n i z e d at different temperatures, q u e n c h e d in w a t e r or cooled in air, aged to m a x i m u m hardness, and then the hardness, tensile strength and y i e l d strength were measured. Thin foils w e r e p r e p a r e d and s t u d i e d in TEM at d i f f e r e n t stages in the process. As expected, d i s p e r s o i d s containing Mn and Cr w e r e observed, and aircooled specimens c o n t a i n e d 8'-Mg2Si-rods. For a i r - c o o l e d alloys h o m o g e n i z e d at 520oc an i n t e r e s t i n g effect was observed. E y e n if the amount of dispersoids v a r i e d by m o r e than a factor 2 w i t h i n the same thin foil, the n u m b e r of 8'-Mg2Si-rods
Q U A N T I T A T I V E STEM-EDS A N A L Y S E S OF THIN WIRE SPECIMENS H.-O Andr~n, M. Hellsing, and H. Nord~n D e p a r t m e n t of Physics, v e r s i t y of T e c h n o l o g y , Sweden
A. H e n j e r e d
C h a l m e r s Uni412 96 Goteborg,
In a S T E M - b a s e d m i c r o a n a l y t i c a l system the lateral r e s o l u t i o n is limited to 10-20 nm by b e a m s p r e a d i n g and the depth r e s o l u t i o n is d e t e r m i n e d by the p e n e t r a t i o n depth of the electrons. This leads to an a v e r a g i n g over not too well d e f i n e d volumes w h e n p e r f o r m i n g analyses w i t h high spatial resolution. It has t h e r e f o r e been found useful to compare the results from this t e c h n i q u e w i t h those from another m i c r o a n a l y t i c a l technique, a t o m - p r o b e m i c r o a n a l y s i s , w h e r e signal g e n e r a t i o n and d e t e c t i o n relies upon other p h y s i c a l principles. Both lateral r e s o l u t i o n and depth r e s o l u t i o n of the atom probe is about 1 nm and the r e l a t i v e s e n s i t i v i t y for d i f f e r e n t atomic species seems to be c o n s t a n t and i n d e p e n d e n t of s p e c i m e n composition. The use of a t o m - p r o b e specimens, s h a p e d as thin tips, in STEM EDX analysis has the added a d v a n t a g e that local s p e c i m e n thickness, depth and size of s p e c i f i c
Abstracts of 34 th Scandinavian Society Annual Meeting
f e a t u r e s a n d t h i c k n e s s of s u r f a c e l a y e r (if p r e s e n t ) c a n b e m e a s u r e d d i r e c t l y .
HIGH
RESOLUTION ELECTRON MICROSCOPY IN M A T E R I A L S S C I E N C E
T H E S T U D Y O F O R D E R E D A L L O Y S BY M E A N S HIGH RESOLUTION ELECTRON MICROSCOPY AND ELECTRON DIFFRACTION* G. v a n T e n d e l o o , S. A m e l i n c k x * *
J.
van Landuyt
OF
and
Laboratorium voor Hoogspanningselektronenmikroskopie, Rijksuniversitair Centrum, B 2020 - Antwerpen, Belgium; * * A l s o at S . C . K . , B - 2 4 0 0 - M o l , Belgium
The instrumental resolution of presentday electron microscopes allows obtaining of atomic resolution under favourable circumstances. The combination of high resolution electron microscopic imaging and selected area electron diffraction h a s p r o v e d to be o f g r e a t h e l p in e l u c i d a t i n g the s t r u c t u r e s o f c r y s t a l s w h i c h are h i g h l y f r a g m e n t e d in s y m m e t r y - r e l a t e d d o m a i n s , s u c h as o r d e r e d a l l o y s . The use of the superlattice reflections either in the d a r k f i e l d o r in t h e b r i g h t f i e l d mode allows revelation preferentially of the c o n f i g u r a t i o n s o f l i g h t m i n o r i t y a t o m s in g o l d m a n g a n e s e a n d g o l d magnesium alloys. In o u r c o n t r i b u t i o n w e d i s c u s s s o m e r e c e n t r e s u l t s o n the i d e n t i f i c a t i o n a n d the s t u d y o f n e w p h a s e s in the A u - M n I a n d the A u - M g 2 s y s t e m s u s i n g t h e d e s c r i b e d techniques. It is s h o w n t h a t s e v e r a l different long period structures may occ u r s i m u l t a n e o u s l y i n the s a m e s p e c i m e n . Very small composition differences apparently induce different structures, the d i f f e r e n c e s in c o m p o s i t i o n b e i n g i n c o r porated along non-conservative anti-phase boundaries. S o m e r e s u l t s o b t a i n e d in t h e s t u d y o f o t h e r a l l o y s a r e d i s c u s s e d b r i e f l y also. R e f e r e n c e s for A u - M n s y s t e m : G. v a n T e n d e l o o , R. w o l f , S. A m e l i n c k x , Phys. Stat. Sol. (a) 40 (1977) 531. G. v a n T e n d e l o o , R. W o l f , D. v a n Dyck, S. A m e l i n c k x , Phys. Stat. Sol. (a) 47 (1978) 105. R. Wolf, G. v a n T e n d e l o o , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. Stat. Sol. (a] 47 (1978) 241. G. v a n T e n d e l o o , R. W o l f , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. S t a t . Sol. (a) 47 (1978) 539. G. v a n T e n d e l o o , S. A m e l i n c k x , Phys. Stat. Sol. (a) 47 (1978) 555. R. W o l f , G. v a n T e n d e l o o , J. v a n L a n d u y t , S. A m e l i n c k x , P h y s . Stat. Sol. (a) 48 (1978) 39.
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G. v a n T e n d e l o o and S. A m e l i n c k x , Phys. Stat. Sol. (a) 49 (1978) 337. G. v a n T e n d e l o o , R. de R i d d e r , S. A m e l i n c k x , Phys. Star. Sol. (a) 49 (1978) 655. G. v a n T e n d e l o o and S. A m e l i n c k x , Phys. Stat. Sol. (a) 51 (1979) 141. G. v a n T e n d e l o o , M. v a n Sande, S. A m e l i n c k x , Phys. Star. Sol. (a) 55 (1979) 681. G. v a n T e n d e l o o , J. v a n L a n d u y t , S. Amelinckx, "Electron Microscopy 1980" ed. P. B r e d e r o o and G. B o o m (7th Eur. Congr. on E l e c t r o n M i c r o s c o p y F o u n d a tion, L e i d e n , 1980) vol. i, p. 226. G. v a n T e n d e l o o , R. W o l f , J. v a n L a n d u y t , S. A m e l i n c k x , Phys. Star. Sol. (a) 60 (1980) 581. R e f e r e n c e s for A u - M g s y s t e m : M. v a n Sande, G. v a n T e n d e l o o , S. A m e l i n c k x , P. Airo, Phys. Stat. Sol. (a) 55 (1979) 681. G. v a n T e n d e l o o , M. v a n Sande, S. A m e l i n c k x , P. Airo, " E l e c t r o n M i c r o s c o p y 1980" ed. P. B r e d e r o o and G. B o o m (7th Eur. C o n g r . on E l e c t r o n M i c r o s c o p y F o u n d a t i o n , L e i d e n , 1980) vol. l, p. 276.
THE CRYSTAL STRUCTURE OF SOME NEW ANTIGORITE MODIFICATIONS A.
Olsen Institute of Physics, O s l o , P. O. B o x 1 0 4 8 ,
University of O s l o 3, N o r w a y
A n t i g o r i t e is a s e r p e n t i n e m i n e r a l with an alternating wave structure. The r e p e a t o f t h e c o r r u g a t i o n is a l o n g t h e A - a x i s w h i c h c a n v a r y f r o m 17 R t o ll0 ~. A n t i g o r i t e is k n o w n t o h a v e a o n e ' l a y e r s t r u c t u r e w i t h C ~ 7.3 ~ a n d B ~ 9 . 3 R. The present paper reports several new modifications of antigorite with 10-1ayer structures. These minerals have been identified by a combination of transmission electron microscopy and diffraction, X-ray powder diffraction and X-ray microanalysis. The distance between the reflections in the A*-direction corresp o n d s t o a s u p e r p e r i o d a b o u t 38 ~ . T h e structure of a 10-1ayer antigorite with c e l l p a r a m e t e r s : A = 3 8 . 1 0 R; B = 9 . 2 4 6 R a n d C = 7 2 . 6 0 ~; ~ 8 = 7 = 90 ° h a s b e e n s t u d i e d in d e t a i l . The number of atoms in t h e u n i t c e l l is a b o u t 2 5 5 0 , a n d ~ e composition can be described by th e formula: (Sgl_x_yFexAly)420 (Sil_zAlz)300 O780+420y~300~ (OH)540-420y+300z w h e r e x < 0.i; 6 < 0 . 0 7 £ z < 0.0~3. By comparing calculated electron 4iffraction
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Abstracts of 34th Scandinavian Society Annual Meeting
patterns from different models with exp e r i m e n t a l patterns, the most probable, ideal structure has been determined. The principles controlling this structure can easily be applied to explain the exist e n c e of the other similar antigorites o b s e r v e d in nature. The main d i f f e r e n c e between these structures is the p o s i t i o n of 4- and 8-membered Si205 rings. SYMMETRY AND S T R U C T U R E D E T E R M I N A T I O N OF B a - N d - T i - O X I D E S BY C O M B I N I N G CBED AND HREM A. Olsen*, R. S. Roth** and P. Goodman*** * I n s t i t u t e of P h y s i c s , U n i v e r s i t y of Oslo, P. O. B o x 1048, O s l o 3, N o r w a y ; * * N a t i o n a l B u r e a u of S t a n d a r d s , W a s h i n g t o n , D.C. 2 0 2 3 4 , U . S . A . ; a n d * * * C S I R O , D i v i s i o n o f C h e m i c a l Physics, P. O. B o x 160, C l a y t o n , V i c t o r i a , A u s t r a l i a 3168.
High resolution lattice imaging ( H R ~ ) is a p o w e r f u l tool to investigate crystal structures in complex oxide systems. Such images can frequently be used on their own to d e t e r m i n e crystal symmetry) this is only o c c a s i o n a l l y p o s s i b l e w h e n a short unit cell axis is parallel to the incident beam. One of the w e a k n e s s e s in this m e t h o d is that asymmetries may be i n t r o d u c e d into the image by asymmetries in the i l l u m i n a t i o n (i.e. a d i s p l a c e d objective aperture) or to i n c o r r e c t or inaccurate crystal alignment. On the other hand, c o n v e r g e n t b e a m d i f f r a c t i o n is an e s t a b l i s h e d means of d e t e r m i n i n g crystal symmetry, free from the above shortcomings, but usually suffers from the weaknesses: (a) the area i l l u m i n a t e d is very large c o m p a r e d w i t h a unit cell and so the data provide@ an average symmetry, and (b) w e a k superstructure reflections are frequently not visible in the CBED pattern. By c o m b i n i n g HREM and CBED many of these w e a k n e s s e s of the individual techniques can be o v e r c o m e or become irrelevant. This has been p a r t i c u l a r l y true in the p r e s e n t study about s y m m e t r y elements, space group and structure of some Ba-Nd-Ti-oxides.
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y D I S L O C A T I O N S AND INTERFACES IN SEMICONDUCTORS
OF
A. Olsen* and J. C. H. Spence** *Institute of Physics, University of o s l o , P. 0. B o x 1 0 4 8 , O s l o 3, N o r w a y ; **Department of Physics, Arizona State U n i v e r s i t y , Tempe, AZ 8 5 2 8 1 , U S A
Structure imaging by high r e s o l u t i o n t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y has given s o l i d - s t a t e chemists and m i n e r a l ogists new insight into many defect structures and phase t r a n s f o r m a t i o n mechanisms in recent years. In the field of s e m i c o n d u c t o r physics, however, there have been few really useful results from this technique. This is chiefly because it is not p r e s e n t l y p o s s i b l e to obtain a s t r u c t u r e image at atomic resolution of any common semiconductor. Here a structure image is defined as a lattice image w h i c h faithfully reveals a crystal's structure to some limited resolution and w h i c h was r e c o r d e d under i n s t r u m e n t a l conditions w h i c h are independent of the structure. Since the information r e s o l u t i o n limit set by electronic i n s t a b i l i t i e s is far below the point r e s o l u t i o n of a m o d e r n t r a n s m i s s i o n microscope, it is p o s s i b l e to obtain, by choice of focus and thickness, clear lattice images both r e s e m b l i n g and not r e s e m b l i n g the true crystal structure. The p r e s e n t paper reports a study of the core structure of d i s l o c a t i o n s in Si and c o m p o s i t i o n a l analysis across interfaces in III-V semiconductors. All the details in the e x p e r i m e n t a l images o b t a i n e d in a JEOL 100B m i c r o s c o p e lie b e y o n d the c o n v e n t i o n a l point r e s o l u t i o n limit. The main part of the paper is concerned w i t h i n t e r p r e t a t i o n of such image details.
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y STUDIES IN THE T U N G S T E N O X Y G E N SYSTEM W u b e s h e t Sahle and M a r g a r e t a S u n d b e r g Department of Inorganic Chemistry, Arrhenius Laboratory, University of Stockholm, S - 1 0 6 91 S t o c k h o l m , Sweden
High r e s o l u t i o n e l e c t r o n m i c r o s c o p y (HREM) technique has b e e n used to characterize d i f f e r e n t phases in the region W02.72 - WO3. 0 of the t u n g s t e n - o x y g e n system. The o r d e r e d and defect structures of the phases w e r e d e t e r m i n e d by means of e l e c t r o n d i f f r a c t i o n p a t t e r n s and from HREM images of thin crystal fragments (thickness < 100 ~). The resolution in the images was ~ 3.5 R. The e l e c t r o n d i f f r a c t i o n p a t t e r n of a crystal gave i n f o r m a t i o n about the average crystal structure, w h i l e the H R E M images gave d e t a i l e d i n f o r m a t i o n about the local crystal s t r u c t u r e of the fragments. The f o l l o w i n g phases w e r e found: {102} c r y s t a l l o g r a p h i c shear (CS) structures (W0~2.93 - WO~3.0) , {103}CS-structures (WO%2.88 - W0~2.93) , and the W2~068 (WO~2.83~ and the W 1 8 0 4 q (WO 2 72 ) structure types . All these s £ r u c t u r e s
Abstracts of 34th Scandinavian Society Annual Meeting are b u i l t up of d i f f e r e n t rather complicated s t r u c t u r e units, and will be exemp l i f i e d by HREM images and s t r u c t u r e models. In the C S - s t r u c t u r e types, twinning, d i s o r d e r and f a u l t i n g in the C S - p l a n e s were f r e q u e n t l y observed. Defects and t w i n n i n g were also found in the W 2 4 0 6 8 - p h a s e , w h i l e W18049 a p p e a r e d to be very well o r d e r e d (with a few exceptions). I n t e r g r o w t h b e t w e e n the various phases has been observed. E x a m p l e s of d i f f e r e n t types of defects and i n t e r g r o w t h are presented. Since defects and t w i n n i n g are freq u e n t l y o c c u r r i n g in this system, the HREM technique has p r o v e d to be an i n v a l u a b l e tool, as a c o m p l e m e n t or substitute to the c l a s s i c a l X - r a y single crystal studies. The W 2 4 0 6 8 structure, of a new type, has i n d e e d been d e t e r m i n e d d i r e c t l y from HREM imagesl since crystals suitable for X - r a y d i f f r a c t i o n w o r k w e r e not a v a i l a b l e 2. i. 2.
s. Berglund and W. J. Sahle, State Ch~m. 36 (1981) 66-73. M. Sundberg, Chemica Scripta (1978-79) 161-66.
Solid 14
HIGH R E S O L U T I O N E L E C T R O N M I C R O S C O P Y A P P L I E D TO T U N G S T E N B R O N Z E S AND ANALOGOUS COMPOUNDS Lars Kihlborg, Sharma
Altaf
Hussain*
and Renu
D e p a r t m e n t of I n o r g a n i c Chemistry, A r r h e n i u s Laboratory, U n i v e r s i t y of Stockholm, S-I06 91 Stockholm, Sweden; *permanent address University of Dacca, B a n g l a d e s h T u n g s t e n b r o n z e s is the name of a group of oxides w i t h the general formula AxWO3, 0 < x < i. In the m o s t typical systems A is an alkali metal. W i t h i n the c o m p o s i t i o n region d i f f e r e n t phases form d e p e n d i n g on x and the size of A. These phases g e n e r a l l y have w i d e h o m o g e n e i t y ranges in x ahd are thus typical n o n s t o i c h i o m e t r i c compounds. They are c h e m i c a l l y very inert and some p o s s e s s very intere s t i n g p h y s i c a l p r o p e r t i e s , .such as high m e t a l l i c conductivity. The t u n g s t e n b r o n z e s are very w e l l s u i t e d for s t r u c t u r e i m a g i n g in an electron m i c r o s c o p e w i t h a b o u t 3.5 ~ resolution. H R E M studies have r e v e a l e d an e x t e n s i v e family of p h a s e s forming w i t h A = K, Rb and Cs for low values of x. These have b e e n n a m e d i n t e r g r o w t h tungsten b r o n z e s (ITB) since £heir structures, as r e v e a l e d by HREM images, can be cons i d e r e d as i n t e r g r o w t h on a unit cell level of WO 3 and one of the o t h e r tungsten bronzes, d e s i g n a t e d HTB (hexagonal
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tungsten bronze). The p r o p o r t i o n of the two s t r u c t u r e elements can vary, w h e r e b y d i f f e r e n t m e m b e r s of this s t r u c t u r e family are formed. Disorder, long-periodic m o d u l a t i o n and various types of defects have also been o b s e r v e d in the images. Recent studies of fully o x i d i z e d analogues, in w h i c h part of the t u n g s t e n has been r e p l a c e d by a p e n t a v a l e n t m e t a l (V, Nb or Ta) have e x t e n d e d the n u m b e r of k n o w n m e m b e r s of the ITB family cons i d e r a b l y and also r e v e a l e d s t r u c t u r e s r e p r e s e n t i n g the extreme ends of this i n t e r g r o w t h range: WO 3 w i t h i s o l a t e d slabs of HTB and vice versa. V e r y comp l i c a t e d i n t e r g r o w t h s e q u e n c e s have also been observed, the o r i g i n of w h i c h is an i n t r i g u i n g question. This s y s t e m thus is an i l l u s t r a t i o n of the great u s e f u l n e s s of the HREM technique in solid state chemistry. The imp o r t a n c e of the m e t h o d w i l l i n e v i t a b l y grow still further as the r e s o l u t i o n of c o m m e r c i a l m i c r o s c o p e s i n c r e a s e s and even d e n s e l y p a c k e d s t r u c t u r e s can be imaged.