Hydrogen vibrations in HxYBa2Cu3O7 superconducting ceramics

Physica C 162-164 (1989) 1369-1370 North-Holland

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~,V. EELUSHKIN, J. BRANKOHSKI, E ~

GORENYCHKI~ J. HAYER, ; J - SASHIN

o f N e u t r o n P h y s i c s , ~INR, 14198Q D u b n l , L_~_.

V~(. FEDOTOV, ~ I . KOLESNIKOV, I ~

BASHKIN, V.V. SINICYN, E ~

PONV~OVSKII

Institute of Solid State Physics, Academy of S c i e n c e s of the USSR, 14E43~ ~her_r~Jg~,_iovKa, USSR

The i n e l l s t i c ~ sclttePing (INS~ and neutron d~fPmction (ND) specb~a from abe HxYBa~ECu307 super~=onducting carlmdcs (x - ~gS, g ~ , g ~ ) I r e investigated i t ~ 8e and 10 ~CVibrational s p e c t r a of h i ~ n a r o m a show t h r u m ~ d e bandm i t a b o u t 1~, 28 a n d 8 ~ m~V. Znt4mm~em o f them a r e tionIL1 t o the h y m n conc~io~ From the t 4 1 m ~ behlviouP of the IN~ ~l=eCt~a a n d f r o m t h e X-ray ~

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Peepond t o i n imoPphou~ not ~pePconducting p r e c i p i t l t l o n ~ ~hieh a r e f o r b a d d u r i n g hydPetltion of Y-I~3 superconducting cePamice~From the cor~antPation d e p e n d e r ~ of t h l INS s ~ e c t ~ we cam c o n c l u d ~ t h l t the solubility of h y ~ in Y-1E3 superconducting phlse is in oPde~ of few percent. It seems t h l t Hi ~ in solid solution ~ locld~d in the o ~ t i ~ position formed by four Y ~ t w o Cu(E) i ~

Effect. o f h y o ~ n a b s o r p t i o n on super-c o n d u c t i v i t yof, HxYBaECu307 compounds h i s been ~gat41d "-'v fop v e r y wide r i m ~ o f h y d r o g e n

v i r t u a l l y constant in t h i s concentration region and the r ~ t a t i ~ volume of superconducting phase decPeimed f r o ~ I~V. t o L~y,. The X-Ply and kID

c o n c e n t r a t i o n • < x < 5 p e r f o r m u l a unit. A sm~LI r e g i o n o f H nM~Ltd s o l u b i l i t y u p t o x ~ 0 ~ was r e p o r t e d . This Pagion remains ~upePconducting

pattarrm prove the orthorombic structure of the sample. A t x - 0 ~ m v t P y mmcLI l n c r ~ m m o f thm p a r ~ m a t 4 ~ • a n d of t h e volume of t h e c a l l wads ~ . t h e (2 G 0) r e f l ~ b r o a d e n s

a slight incPeime of cPiticid tempe~tuPeI . However, i t is a t p r e s e n t f i r from c l e a r whether the hydrogen atoms a r e held n e a r some p a r t i c u l a r surface o r in the bulk . At higher content of H imor~ p r e c i p i t l t e s r i c h of hydrogen, which ape not superconductln~ a r e forme~ The aim o f o u r ~ o r t ( was t o m e a s u r e t h e fr~FJenci~m of the h y d r o g e n aroma v i b r a t i o n s so~Ld s o l u t A o n a n d t o d ~ t e r n d n e t h e h y d r o g e n

significantly with anti-ease of hydrogen c o n c l n trcrtion, in comparison with the (e ~ e) reflex. ~

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atoms positions in the c r y s t a l l i n e stPuctur~ of HxYBa2Cu3D7 . The originad YBa2Cu307 cmramics simple wls produced tPom Y~O3 , BiO and CuO using the standard p o w d e r metidlurgy ¢achniclue. Transition temperature measured by the magnetic susceptibility mathod was T¢ = 92 K with AT - 5 K. The hydrogen idoeoPption was c a r r i e d out a t t e m p e r l t u r e equal t o leg°C and a t pressure ~.8 - 1,¢ atnt The concentration of absorbed hydrogen was determined by measuring the c h l r ~ of the pressure in abe given volume. The neulron scattering experiment wls performed f o r the o r i g i n a l s a m p l e a n d f o r t h r e e different concent~ations of absorbed hych-oger~ ,x = ~.~5, ~ and ~ . The tr~nsltion temperature

0921--4534/89/$03.50 © Elsevier Science Publishers B.V. ( North-Holland )

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o neutron wovelength (A) Fig. 1. INS s p m c t r ~ o f HxYBaeCu306.95 s u p t P conducting cePmnics fop dtffar~lnt hyctrogan c o n c B n t r a t L o n ~ The t4~mctP#m m - e n o r m a l i z e d

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I. Natkaniec et al. I Hydrogen vibrations in HxYBa2Cu~07 superconducting ceramics

1370

NI~n Iclitter-ing I x p I ~ i m l n t was clr`r`ied out lit ~ I ~ -I~ high flUX ~I~Ilid rllliCtor`5 using the KDSOG-M t i m e - o f - f l i g h t invIr`ted g~omItey spectrometer" 6 . The normalized INS s ; ~ l i for diffIr`Int c o r ~ : i n t r l t i o n i of hydrogen ==re s h o ~ n in Fig. L The a~)sorbII~ hydt'ogen s p e c t r l w e r e a b t a i n l d b y s u b t r a c t i n g the s p e c t r u m of o r i g i n a l Ili~lI frOlll t h l h y c h ~ l ' ~ J s ones. The r-estLtting

specteli a r e shown in Fig. E. The i n t e ~ l intinsity of ~clitteN~d ~ n s i n c r e m pr~=;=or`tion~1ly t o the c o n c i n t r l i t i o n of the hydrogen atoms in the I ~ | I . From the INS s p e c t r a in Fig. ~, th~ am~:~litudI ~ i l g h t l d h y c h ~ vlb~i~ c/nIity of s t a t e s ~ I r e c l i l c u l l i t ~ d l i c c a ~ d i n g t o the f o r mula d e s c r i b i n g on~-l:#~non i n c o h e r e n t n e u t r o n s c a t t e r i n ~ They a r e shown in Fig, Three bands l i t about 14, ~8 lind 85 meV with intensities incrIIliIing l:w~=~=~tioily to hydrogen c o n c e n t r a t i o n a r e o b s e r ~ The high frequency band n a r r o w s , becomes more Intens~ and l h i f t i t o higher- f r e q u e n c i e s with dIcreau~ing temper`litur~i. On the other` hand i t shift~ t o lower` fr~r~II with Increesing con~inta-litior~ This behaviou~ does not cor`rel~rte well with the X-rliy a n d n e u t r o n dlff~liction mem~ur~imInts for` o u r I i a n l l ~ l I . The obt~i.ned l l i t t i c e p l i t ' ~ i r e virtuli1~ c o l t in lippli~d temp~rliture a n d c o n c e n t r a t i o n r~nge, No l i d d l t i o n a l d i f f r a c t i o n ma~im~, i n d i c a t i n g t h e I ~ i l t e n c l i of ~ phil, wera o b s e r v i ~ i Thus one (::an conclude t h a t these bands c o r r ~ i p o n d t o H v i b r l i t i o n s in r i c h of hydrogen amorphouI p r e c i p i t ~ t i o n ~ In Fi~ 3 Ohm c a n m a ~ d i t i o n a l b i n d s l i t about 24, 36 ~ 7@ meV, for` x I @.@5. They , , r e L t s o p r e s e n t in the P D O S of YBaECu307 and c o r r e s pond t o Y ~toms and Cu(2)-O p l a n t s v i b r e t i o n s7-9. --o~ J ' I I

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Fi~ 3, Amplitude weighted hydrogen vilm-ition diInsity of s t a t e s in HxYBI2Cu3Q695 for` x " @.@5, @ ~ @ a n d @~@, normalized to 1@@@ a t maximumof e n e r g y distr`ibutior~ The f a c t t h a t n e u t r o n intensity of this type of v i b r a t i o n s only i n c r ~ I I i e s indicates t h a t hydrogen pr~Ifer`ably occupies the o c t a h i d r ~ l s i t e HII3 , In this position li hydrogen ~ is s u r r ~ a ~ i d by f o u r Y and two Cu(E) ~ From the f a c t t h a t the i n t e n s i t i e s of these b i n d s do not i n c r e a s e pr~:)por`tlonally t o h y d r o g e n c o n c e n t r l i t i o n one can conclude t h a t the s o l u b i l i t y of H in super-conducting p h a i e of YBa~Cu307 i s in order- of f~ra p e r ~ I n t only. REFERENCES 1. J~. RIilly, ht Suenaga, Ja~ Fohnson a t a l , PhyL Rev. 36B (1987) 5694.

3, H, F u j i l , H. KawlirIK~, H, Ym I t al., Jap~ J. of AppL PhyI, 27 (1988) L525.

20000

4. I'I. N i c o l a l , J ~ Daou, L. VIckIl e t If., Solid State Commur~66 (1988) 1157.

:~15000

5. V.D. Ananev, V,4. ArKhipov, ~ Bunin I t al., Inst. Phys. Conf. N r 64 (1983) 4q7.

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2. C,Y. Yan~ X~L Y ~ ~ Head a t al., Phys. RIv. 3bB (1987) 8798,

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(~ Balul(a, A.V. Belush~n, SJ. Bragin at. aL, R e p o r t JINR hh- P13-84-242, Dubna 1984.

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7. I. NatKanlec, A,V. BelushKin e t al., JETP Lett, 48 (1988) 181.

neutron wavelength (~)

Fi;k E. Intensity of the n e u t r o n s I ~ l i t ~ hych'-ogen in HxY'B~L:CU30(:~5 for`" x @.2@ ~ n d @.6@ l i t T = ~ K.

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8. hta~ Cr~wfor-ck ~E. Far`net,s, EJ~. McCarron I l l and RJ(. Sordia. Phy~ Rev. 3gB (1988) 11382. 9. F J=. B i t e s , Phys. Rev 39B (1989) ~ .