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Research on some IR transmission halide glass systems
Journal of Non-Crystalline Solids 56 (1983) 69-74 North-HoUandPublishing Company
69
RESEARCH ON SOME IR TRANSMISSION HALIDE GLASS SYSTEMS Jiang Zhonghong, Hu Xinyuan, Song Xiuyu, Zhao Xiangshu Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, P.R.C.
In order to find new IR transmission halide glass systems, we have prepared several hundred compositions of halide glass. The glass formation regions have been studied in a large number of ternary systems. Based on the behavior of the glass-formation regions some principles about halide glass formation were discussed. The crystallisation characteristics of halide glasses were studied by DTA, X-ray diffraction and SEM. Some comparatively stable glasses have been prepared. I. INTRODUCTION With the development of infrared techniques, laser and IR optical fiber materials, fluoride and other halide glasses have been receiving considerable interest. A great number of new qlasses in these systems have already been made and investigated [I-4] . In the present work, emphasis is placed on examining the glass formation behavior of halide systems and drawing some general rules from the experimental results in order to predict the glass formation regions of some new systems. The purpose is to minimize the experimental work needed to select IR glass compositions suitable for large scale production. In our research work, studies on the spectral properties, structural characteristics and other physical properties have been performed in many halide systems. Only the glass formation behavior of some systems and the IR transmittance of some new glasses are described in this paper and the rest will be described at a later date.
[I. GLASS FOR~iATION BEHAVIOR OF HALIDES I. The coordination number and neutralization of electric valence. Halide glass formers, similar to the oxides, all have mixed chemical bonds, and can be divided into the following three groups: (I) Those with a coordination number of 4 (Kz=4) and a neutralized electric valence, e.g. BeF 2 ,ZnC12 ZnBr 2 etc. They can form stable glass and, when a second component is introduced, the glass formation region is increased. (2) Those with a coordination number of 4 (Kz=4),but a unneutralized electric valence, e.g. AlP 3 etc. They can also exhibit a coordination number of 6 (Kz=6) , but they can not form stable glass alone unless special high speed quenching is employed. Only when a second component is introduced to neutralize the residual electric 0022-3093/83/0000-0000/$03.00 © 1983 North-Holland
70
Jiang Zhonghong et al. / IR transmission halide glass systems
valence, can the structural units link through their vertexes to form a network structure. (3) Those with a coordination number of 6 (KZ=6) and a unneutralized electric valence, e.g. ZnF2 , ZrF 4 , ThF 4 , HfF 4 , ThC14 etc. Their glass formation behavior is similar to group II. By comparing the structures of other comounds with those of the above three groups• new glass formers and new glass systems can be deduced. 2. The location of eutectics As in oxide systems, eutectics playing an important role in glass formation in halide systems are all located between the positions where the network former-to-network modifier ratio are 3:1, 2:1 and 1:1 [5~. Therefore, glass formation regions are most probably located near the point where the glass former halide content is 60mo1.% . Since glass formation regions will extend toward the directions of 45 mol.% or 70 mol.% network formers because of the influence of the location of eutectics, the most promising glass formation region in a ternary system can be p r e d i c t ed using the knowledge about the eutectics of the related binary systems. 3. The quantitative calculation of eutectics Calculations were carried out on the phase diagrams of various kinds of binary systems using the available thermodynamic data, such as melting points and fusion heats• of the related components. As a result, it was found that the location of eutecties have no significant variation[6,7]. Hence, it would be reasonable to estimate the rough location of eutectics based on the related thermodynamic data of halides. 4. The effect of phase separation on the glass formation behavior of halides There has not been much research work to date on the phase separation in halide glass systems. According to Imaoka [8J and Vogel [9] , in the binary and ternary system glasses containing BeP2, phase separation would occur in the high network former regions. Some studies on the multicomponent glass systems containing ZrF 4. ThF 4 , ZnF2 and PbF2 suggest that transparent glasses could not be formed in the high network former regions and this was ascribed to phase separation and crystallization. From the above viewpoints, the glass formation behaviour of halides can be summarized graphically as follows: In Fiqure I where Nf1: KZ=4, Nf2:Kz =6 or 4 with electric valence unneutralized, NM: network modifier including NMI: halides of monovalent metals and Ba and Sr, NM2: halides of Ca, Mg and trivalent metals. III. EXPERIMENTAL According to the above considerations, experiments were made on several hundred compositions of halide systems. A large number of binary and ternary glass formation systems were established, since the glass formation regions can be easily determined with only a few experimental runs using the conventional visual method. The starting materials used were fluorides• chlorides and a few bromides. They are all CP or AR grades. Among them, ZrF 4 and HfF 4 were prepared and purified in our own laboratory. All the raw-materials were heated and dehydrated under an Ar atmosphere and the fluorides were identified by X-ray diffraction and chemical analysis to be 98.3% pure or better. Two different procedures were employed to prepare the glasses: (I) Using graphite crucible and under NH4C1 and NH4F.HF atmospheres
71
Jiang Zhonghong et al. / IR transmission halide glass systems
Xfl
Kt'I
*N[1
/
\ /
\ /
\
/
\
\ /
\
!
N.II1
N J/, X511
N31~ X.~l2
N.~I;
Figure I Predicting Typical Halide Glass Formation Range Stable Glass Range ..... Unstable Glass Range (2) P l a t i n u m crucible and Ar atmosphere. Glasses ana crystals u O tained w i t h the above two methods were c o n f i r m e d by X-ray diffraction and DTA to be reasonably similar. The first m e t h o d was used mainly to d e t e r m i n e the glass formation regions. In every e x p e r i m e n t a l run, 3g Of glass was melted. To accelerate cooling of the melts, they were poured onto a m e t a l l i c plate and p r e s s e d with a copper plate. The shapes of the glass form a t i o n regions e s t a b l i s h e d are a p p r o x i m a t e l y the same as those p u b l i s h e d in the literature, though some d i s a g r e e m e n t was found due to the d i f f e r e n c e s in the cooling rate and in the sample size. Only those glass formation regions of some ternary systems that have not been reported in the literature are shown in Fig. 2 and Table I b e c a u s e of the limited space. It was also found that some glass melts of higher PbF 2 content are apt to become y e l l o w and crystallize after b e i n g cast. This made it impossible to judge the role of PbF2 in the glass formation. In addition, chloride and bromide glasses were d e l i q u e s c e n t and a thin w h i t e opaque layer formed on the surface of the melts cooled in air. The poor chemical d u r a b i l i t y of these glasses did not seem to influence their glass formation capabilities. Figure 4 is the IR t r a n s m i t t a n c e curves of ZrF 4 and BaF 2 glasses w h i c h were m e l t e d in p l a t i n u m crucibles and can likely De manufactured on a larger scale. Figure 3 shows the DTA curves and some crystal products of halide glasses.
72
Jiang Zhonghong et aL / IR transmission halide glass systems
AAAAAA/VVV~ 8rF2
PbF~
( 'a l&
=
PbCI~
B~F~ - - - - - -
"
/; a ]VVVVVVV~ I'VVVVVVW\ Lal:~
/ V V V ~ "
/VWVVVV"V~ ~,AAA/\AA AAA
=
B iCl~
*
~
ll,zF,
=
Figure 2 Halide Glasses Formation Range o transparent glass . opaque glass Table I
No
ZrF 4
BaF 2
Composition of Halide Glasses composition mol.% SrF 2 LaP 2 CaF 2 ZnC12 NdF 3 CeF 3 BiC13 Tg°C Tc°C
I 65 3O 5 2 70 30 3 75 25 4 62 30 5 60 22 12 6* 61.18 29.61 3.54 7 62 33 8 50 40 9 65 30 10" 61 29.52 wt%
8 6 1.89
1.89
I~89
5 10 3.82
5 4.72
0.94
295 280 290 330 315 315 310 310 310 315
35O 340 340 385 370 380 360 360 350 370
73
Jiang Zhonghong et al. / IR transmission halide glass systems
350 350
cryst, in No. 4 320 x cross
5oo 580
[
525
2
630 cryst.in No.7 320 x parallel
o
cryst.in No.8 150 x parallel
m
0
Z
7
cryst.ln No.9 150 x parallel
350 575 625
k..
575
temperature
10
°C
I
,
,
•
10
i
,
.
I
.
.
.
.
.
.
.
.
.
20
Figure 3 DTA curves (left) of glasses in Table I. Crystals present in glasses shown in upper right and x-ray diffraction pattern for y-ZrF 4 lower right.
I
I
I
20
74
Jiang Zhonghong et al. / IR transmission halide glass systems
100
I
3
4
5
'
'
'
6
7
8
'
,
9 10 12 ,
16 A ~
,
•
.
0 .,4 tO ~n
.~= co g¢
0 I
4000
3000
I
I
I
I
2000 1'800 1600 1400
I
I
I
1200 lOO0 SO0
I
cm
-I
Figure 4 The IR Transmission Curve of the Glasses I (sample 10 thickness:0.4mm) 2 (sample 6 thickness:O.5mm) LITERATURE [1! Sun K.H. "Fluoride glasses", Glass Techn., 20 (~979) 36-. [25 Angell C.A., Ziegler D.C., "Inorganic chloride and mixed halide glass with low maximum phoncn frequencies", Mat. Res. Bull., 16 (1981) 279-. [3] Lucas J., Chanthanashik M., et al., "Preparation and optical properties of deodymium fluorozirconate glasses", J. Non-Cryst. Solids, 27 (1978) 273-. [4] Hu Hefang, Ma Fuding, Mackenzie J.D., "New halide glassesbromide glasses based on ZnBr 2 (I) Vitreous Zinc Bromide" (in press) [5] Jiang Zhonghong, "Some aspects on regions of glass formation and devitrification of glasses", J. Chinese Silicate Soc., 9 (1981) 323-. [61Jiang Zhonghong, Xu Xinyuan, Zhao Xiangshu, "Prediction of eutectics and phase separation in the glass formation range using a thermodynamic Method". Non-tryst. Solids, 52 (198~ 235. [7] Jiang Zhonghong, Guo Yanhua, "Using Gibbs free energy to predict the eutectics of inorganic salts and metaphosphates" (to be publish in Bull. of the Chinese Silicate). [8] Imaoka, Mizurawa S., "Studies on fluoride glass (I)", J. Jap. Cer. Soc., 61 (1953) 21-. [91 Vogel W., Struktur und Kristallisation der Gl~ser, 33-40, (VEB Deutscher Verlag fur Grundstoffindustric Leipzig 1965).
69
RESEARCH ON SOME IR TRANSMISSION HALIDE GLASS SYSTEMS Jiang Zhonghong, Hu Xinyuan, Song Xiuyu, Zhao Xiangshu Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, P.R.C.
In order to find new IR transmission halide glass systems, we have prepared several hundred compositions of halide glass. The glass formation regions have been studied in a large number of ternary systems. Based on the behavior of the glass-formation regions some principles about halide glass formation were discussed. The crystallisation characteristics of halide glasses were studied by DTA, X-ray diffraction and SEM. Some comparatively stable glasses have been prepared. I. INTRODUCTION With the development of infrared techniques, laser and IR optical fiber materials, fluoride and other halide glasses have been receiving considerable interest. A great number of new qlasses in these systems have already been made and investigated [I-4] . In the present work, emphasis is placed on examining the glass formation behavior of halide systems and drawing some general rules from the experimental results in order to predict the glass formation regions of some new systems. The purpose is to minimize the experimental work needed to select IR glass compositions suitable for large scale production. In our research work, studies on the spectral properties, structural characteristics and other physical properties have been performed in many halide systems. Only the glass formation behavior of some systems and the IR transmittance of some new glasses are described in this paper and the rest will be described at a later date.
[I. GLASS FOR~iATION BEHAVIOR OF HALIDES I. The coordination number and neutralization of electric valence. Halide glass formers, similar to the oxides, all have mixed chemical bonds, and can be divided into the following three groups: (I) Those with a coordination number of 4 (Kz=4) and a neutralized electric valence, e.g. BeF 2 ,ZnC12 ZnBr 2 etc. They can form stable glass and, when a second component is introduced, the glass formation region is increased. (2) Those with a coordination number of 4 (Kz=4),but a unneutralized electric valence, e.g. AlP 3 etc. They can also exhibit a coordination number of 6 (Kz=6) , but they can not form stable glass alone unless special high speed quenching is employed. Only when a second component is introduced to neutralize the residual electric 0022-3093/83/0000-0000/$03.00 © 1983 North-Holland
70
Jiang Zhonghong et al. / IR transmission halide glass systems
valence, can the structural units link through their vertexes to form a network structure. (3) Those with a coordination number of 6 (KZ=6) and a unneutralized electric valence, e.g. ZnF2 , ZrF 4 , ThF 4 , HfF 4 , ThC14 etc. Their glass formation behavior is similar to group II. By comparing the structures of other comounds with those of the above three groups• new glass formers and new glass systems can be deduced. 2. The location of eutectics As in oxide systems, eutectics playing an important role in glass formation in halide systems are all located between the positions where the network former-to-network modifier ratio are 3:1, 2:1 and 1:1 [5~. Therefore, glass formation regions are most probably located near the point where the glass former halide content is 60mo1.% . Since glass formation regions will extend toward the directions of 45 mol.% or 70 mol.% network formers because of the influence of the location of eutectics, the most promising glass formation region in a ternary system can be p r e d i c t ed using the knowledge about the eutectics of the related binary systems. 3. The quantitative calculation of eutectics Calculations were carried out on the phase diagrams of various kinds of binary systems using the available thermodynamic data, such as melting points and fusion heats• of the related components. As a result, it was found that the location of eutecties have no significant variation[6,7]. Hence, it would be reasonable to estimate the rough location of eutectics based on the related thermodynamic data of halides. 4. The effect of phase separation on the glass formation behavior of halides There has not been much research work to date on the phase separation in halide glass systems. According to Imaoka [8J and Vogel [9] , in the binary and ternary system glasses containing BeP2, phase separation would occur in the high network former regions. Some studies on the multicomponent glass systems containing ZrF 4. ThF 4 , ZnF2 and PbF2 suggest that transparent glasses could not be formed in the high network former regions and this was ascribed to phase separation and crystallization. From the above viewpoints, the glass formation behaviour of halides can be summarized graphically as follows: In Fiqure I where Nf1: KZ=4, Nf2:Kz =6 or 4 with electric valence unneutralized, NM: network modifier including NMI: halides of monovalent metals and Ba and Sr, NM2: halides of Ca, Mg and trivalent metals. III. EXPERIMENTAL According to the above considerations, experiments were made on several hundred compositions of halide systems. A large number of binary and ternary glass formation systems were established, since the glass formation regions can be easily determined with only a few experimental runs using the conventional visual method. The starting materials used were fluorides• chlorides and a few bromides. They are all CP or AR grades. Among them, ZrF 4 and HfF 4 were prepared and purified in our own laboratory. All the raw-materials were heated and dehydrated under an Ar atmosphere and the fluorides were identified by X-ray diffraction and chemical analysis to be 98.3% pure or better. Two different procedures were employed to prepare the glasses: (I) Using graphite crucible and under NH4C1 and NH4F.HF atmospheres
71
Jiang Zhonghong et al. / IR transmission halide glass systems
Xfl
Kt'I
*N[1
/
\ /
\ /
\
/
\
\ /
\
!
N.II1
N J/, X511
N31~ X.~l2
N.~I;
Figure I Predicting Typical Halide Glass Formation Range Stable Glass Range ..... Unstable Glass Range (2) P l a t i n u m crucible and Ar atmosphere. Glasses ana crystals u O tained w i t h the above two methods were c o n f i r m e d by X-ray diffraction and DTA to be reasonably similar. The first m e t h o d was used mainly to d e t e r m i n e the glass formation regions. In every e x p e r i m e n t a l run, 3g Of glass was melted. To accelerate cooling of the melts, they were poured onto a m e t a l l i c plate and p r e s s e d with a copper plate. The shapes of the glass form a t i o n regions e s t a b l i s h e d are a p p r o x i m a t e l y the same as those p u b l i s h e d in the literature, though some d i s a g r e e m e n t was found due to the d i f f e r e n c e s in the cooling rate and in the sample size. Only those glass formation regions of some ternary systems that have not been reported in the literature are shown in Fig. 2 and Table I b e c a u s e of the limited space. It was also found that some glass melts of higher PbF 2 content are apt to become y e l l o w and crystallize after b e i n g cast. This made it impossible to judge the role of PbF2 in the glass formation. In addition, chloride and bromide glasses were d e l i q u e s c e n t and a thin w h i t e opaque layer formed on the surface of the melts cooled in air. The poor chemical d u r a b i l i t y of these glasses did not seem to influence their glass formation capabilities. Figure 4 is the IR t r a n s m i t t a n c e curves of ZrF 4 and BaF 2 glasses w h i c h were m e l t e d in p l a t i n u m crucibles and can likely De manufactured on a larger scale. Figure 3 shows the DTA curves and some crystal products of halide glasses.
72
Jiang Zhonghong et aL / IR transmission halide glass systems
AAAAAA/VVV~ 8rF2
PbF~
( 'a l&
=
PbCI~
B~F~ - - - - - -
"
/; a ]VVVVVVV~ I'VVVVVVW\ Lal:~
/ V V V ~ "
/VWVVVV"V~ ~,AAA/\AA AAA
=
B iCl~
*
~
ll,zF,
=
Figure 2 Halide Glasses Formation Range o transparent glass . opaque glass Table I
No
ZrF 4
BaF 2
Composition of Halide Glasses composition mol.% SrF 2 LaP 2 CaF 2 ZnC12 NdF 3 CeF 3 BiC13 Tg°C Tc°C
I 65 3O 5 2 70 30 3 75 25 4 62 30 5 60 22 12 6* 61.18 29.61 3.54 7 62 33 8 50 40 9 65 30 10" 61 29.52 wt%
8 6 1.89
1.89
I~89
5 10 3.82
5 4.72
0.94
295 280 290 330 315 315 310 310 310 315
35O 340 340 385 370 380 360 360 350 370
73
Jiang Zhonghong et al. / IR transmission halide glass systems
350 350
cryst, in No. 4 320 x cross
5oo 580
[
525
2
630 cryst.in No.7 320 x parallel
o
cryst.in No.8 150 x parallel
m
0
Z
7
cryst.ln No.9 150 x parallel
350 575 625
k..
575
temperature
10
°C
I
,
,
•
10
i
,
.
I
.
.
.
.
.
.
.
.
.
20
Figure 3 DTA curves (left) of glasses in Table I. Crystals present in glasses shown in upper right and x-ray diffraction pattern for y-ZrF 4 lower right.
I
I
I
20
74
Jiang Zhonghong et al. / IR transmission halide glass systems
100
I
3
4
5
'
'
'
6
7
8
'
,
9 10 12 ,
16 A ~
,
•
.
0 .,4 tO ~n
.~= co g¢
0 I
4000
3000
I
I
I
I
2000 1'800 1600 1400
I
I
I
1200 lOO0 SO0
I
cm
-I
Figure 4 The IR Transmission Curve of the Glasses I (sample 10 thickness:0.4mm) 2 (sample 6 thickness:O.5mm) LITERATURE [1! Sun K.H. "Fluoride glasses", Glass Techn., 20 (~979) 36-. [25 Angell C.A., Ziegler D.C., "Inorganic chloride and mixed halide glass with low maximum phoncn frequencies", Mat. Res. Bull., 16 (1981) 279-. [3] Lucas J., Chanthanashik M., et al., "Preparation and optical properties of deodymium fluorozirconate glasses", J. Non-Cryst. Solids, 27 (1978) 273-. [4] Hu Hefang, Ma Fuding, Mackenzie J.D., "New halide glassesbromide glasses based on ZnBr 2 (I) Vitreous Zinc Bromide" (in press) [5] Jiang Zhonghong, "Some aspects on regions of glass formation and devitrification of glasses", J. Chinese Silicate Soc., 9 (1981) 323-. [61Jiang Zhonghong, Xu Xinyuan, Zhao Xiangshu, "Prediction of eutectics and phase separation in the glass formation range using a thermodynamic Method". Non-tryst. Solids, 52 (198~ 235. [7] Jiang Zhonghong, Guo Yanhua, "Using Gibbs free energy to predict the eutectics of inorganic salts and metaphosphates" (to be publish in Bull. of the Chinese Silicate). [8] Imaoka, Mizurawa S., "Studies on fluoride glass (I)", J. Jap. Cer. Soc., 61 (1953) 21-. [91 Vogel W., Struktur und Kristallisation der Gl~ser, 33-40, (VEB Deutscher Verlag fur Grundstoffindustric Leipzig 1965).