ELSEVIER

July 1995

Materials Letters 24 ( 1995) 207-210

Formation and properties of glasses in the systems Bi203-PbO-( ZnF2, CdF2)

Jie Fu Research Institute, OHARA Inc., l-15-30 Oyama, Sagamihara-shi, Kanagawa 229, Japan

Received 17 January 1995; revised 25 April 1995; accepted 27 April 1995

Abstract

Glass forming regions in the systems Biz03-PbO-ZnF, and Bi,O,-PbO-CdF, have been determined. A wide glass forming region occurs in the latter system. The addition of ZnO to this system significantly improves glass stability and clear glass can be easily obtained from a 300 g batch. Glass transition and crystallization temperatures are in the range 290-330°C and 340- 37O”C, respectively. On increasing CdFz content, the ultraviolet absorption edge shifts toward shorter wavelength while the infrared cutoff shifts toward longer wavelength. The glasses have a wide transparent region from 400 nm to 11 p,m.

1. Introduction

A number of studies of B&O,-based oxide glasses, which do not contain any conventional network former, have been reported [ l--5]. These glasses are candidates for infrared transmitting materials due to their long infrared cutoff wavelengths in excess of 9 pm. They are also of interest for applications in ultra-fast all-

optical switches due to their high third-order nonli- nearity [ 51. However, most of these glasses have poor

thermal stability, not permitting the fabrication of large preforms, and the chemical durability is also poor. So, the applications of these glasses would be restricted. Until now, to the present author’s knowledge, there has been no study on Bi,O,-based glasses in which fluorine is incorporated. Therefore, it is interesting to study how the vitreous state may be stabilized and how the prop- erties of glasses are influenced by fluorine if such glasses can be obtained. In the present work, ZnF, and CdF, were introduced into the Biz03-PbO system, respectively. Glass forming regions in both ternary sys-

tems, B&O,-PbO-ZnlF, and Bi,O,-PbGCdF,, were

determined. Some properties of the glasses will be pre- sented.

2. Experimental procedure

Reagent grade chemicals of Bi203, PbO, ZnF, and CdF, were used as starting materials. Batches of 6 g

were employed to investigate the glass forming region.

The batches were placed in platinum crucibles and melted at 1000°C for 20 min in an electric furnace. The

melt was poured onto a stainless steel plate and quickly pressed by another one. The quenched melts were clas- sified into glass, partial devitrification and full devitri- fication based on X-ray diffraction analyses. When preparing glasses using more than 200 g batch size, the melt was cast into a stainless preheated mould and annealed around the glass transition temperature (T,) for 1 h.

DTA was used to determine Tg and the onset crys- tallization temperature (TX). The heating rate was 10°C/min. Thermal expansion coefficient was

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208 .I. Fu /Materials Letters 24 (I 995) 207-210

measured on a 4.0 X 4.0 X 43 mm bar using horizontal vitreous silica dilatometer with a heating rate of 4”C/

min. Density was measured using the Archimedes method with kerosene as the immersion fluid. Refrac-

tive index was determined for a prismatic sample with vertical angle of 45” using the minimum deviation

method [ 61. Some glasses were polished and served for the meas-

urement of transmission spectra in the range 300-700

nm and 400-4000 cm-‘, respectively. Water and acid durabilities were determined by

measuring the weight loss of glass powder after soaking in the distilled water or 0.01 N HN03 for 1 h at 100°C.

3. Results and discussion

Fig. 1 shows glass forming regions in the systems B&O,-PbO-ZnF, (Fig. la) and Bi,O,-PbO-CdF, (Fig. lb). The glasses obtained were light yellow to

8’24

PbO 20 40 60 80 mol%

a24

ZnF2

(b)

PbO 20 41 60 80 CdF2 mol%

Fig. 1. Glass forming regions in the systems (a) BiZO,-PbO-ZnF2 and (b) B&O,-PbG-CdF,. ( 0) : glass, ( 8 ) : partial devitrification,

(0): full devitrification.

reddish in color, depending on Bi,O, content. The glass forming region in the former system is much smaller

than that in the latter system and a large difference in location of the glass forming region is seen; the glass forming region of the former system is located on the Bi,O,-rich side while that of the latter system on the

CdF,-rich side. Dumbaugh [ I] investigated glass formation in the oxide system Bi203-PbO-CdO using

about 5 g of batch. He obtained only partial glasses in the compositional range of 30-90 mol% B&O,. The

observation of large glass forming region by substitut-

ing Cd0 for CdF, in the present study, therefore, sug- gests that the fluorine might play a role promoting glass

formation. No study on property was conducted in the system

Bi,03-PbO-ZnF2 since the glass forming region is small. The following results were obtained from the system Bi203-PbO-CdF,. The glass transition temper- ature ( r,) was clearly observed in almost all the glasses

indicated by the open circles in Fig. lb. The value ranged from 290 to 330°C. There were two crystalli- zation peaks in the DTA curve and the onset crystalli-

zation temperature (TX) corresponding to the first peak

was in the 330-370°C range. The difference TX - T, is in the range of 40-65°C. Effect of CdF, content on T,

is shown in Fig. 2. It is seen that replacing PbO by CdF,

results in an increase in Tg. Replacing Bi203 by CdF, also results in an increase in Tg. Thus, it is suggested that Tg of the glasses is mainly determined by the CdF2

content. Fig. 3 shows the visible spectra of

30Bi,03. 30PbO. 40CdF, glass (Fig. 3a) and 20Bi,O,. 3OPbO. SOCdF, glass (Fig. 3b). Ultraviolet

absorption edge occurs at about 400 nm and it shifts

280

260 - 20 30 40 50 60 70

x (mol%)

Fig. 2. Effect of CdFz content on Tg of 30BiZ03. (70 -x)PbO.xCdF~

glasses.

J. Fu/Materials L.&ten 24 (1995) 207-210 209

100

80

z g 60

5 .z E 6 40

C

20

0

b a

kYl I

400 450 500 550 600 650 700

Wavelenath (nm)

Fig. 3. Visible transmission spectra of (a) 3OBi,O,. 30Pb0.40CdFz

glass and (b) 20Bi203~30Pb0~50CdF, glass. Thickness of both

glasses is 0.6 mm.

toward shorter wavelengths as CdF, replaces B&O,. No obvious absorption is present. In B&O,-based oxide glasses, however, there exists a strong absorption in the range 470-600 nm due to the platinum contamination

[ 21. Absence of such absorption in the present glasses hence indicates that the contamination is suppressed by introducing large amount of fluorine to the oxide sys-

tem. Fig. 4 shows the typical infrared transmission spec-

tra of 30Bi203. 30PbO * 40CdF, glass (Fig. 4a) and 20Bi,O, * 3OPbO. SOCdF, glass (Fig. 4b) . It is seen

that these glasses exhibit very high transmission over 70% in the region of 3.5-7.5 pm. The absorption peak at about 3.0 pm is due to water resulting from starting materials. The cutoff wavelength of the glass in Fig. 4a

Wavelength (pm)

4000 3000 2000 1500 1000

‘Wavenumber (cti’)

Fig. 4. Infrared transmission spectra of (a) 30Bi,O,. 30Pb0.40CdFz

glass and (b) 20Bi203~30Pb0.50CdF, glass. Thickness of both

glasses is 0.6 mm.

Fig. 5. 30Biz03. 2OPbO. lOZn0. 40CdF2 glass sample. The glass is

yellowish in color.

Table 1

Some properties of 30Bi,Os. 2OPbO. lOZnO.40CdF, glass

Properties Values

Density (d)

Refractive index ( nd)

Abbe number ( vd)

Wavelength at transmittance of 50% (5 mm

thickness)

7.93 g/cm3

2.11

15.7

7.0 pm

Glass transition temperature (T,) 310°C

Crystallization temperature (T,) 498°C

Melting temperature (T,,,) 545°C

Thermal expansion coefficient (a) 170x lo-‘K

Water durability at 100°C (R,) 0.09% Acid durability at 100°C (R,) 0.43%

is located at 10 p_rn and it is extended to 11 pm by substituting B&O3 for CdF*. Thus, From Fig. 3 and Fig. 4 it can be concluded that increasing the content of fluorine is effective in obtaining better transmission in both visible and infrared regions. Comparing with the Bi,O,-based oxide glasses with almost the same thickness reported so far [2,3], it is found that the present glasses show the widest transparent region.

210 .I. Fu/Materials Letters 24 (1995) 207-210

Large size of glasses could not be obtained because of their poor thermal stability. In order to improve the thermal stability of the glass, ZnO was introduced into the Bi,O,-PbO-CdF, system. It was found that the glass with composition 30Bi,O, . 20PbO . lOZn0 . 40CdF2 was the most stable and a large sample of glass could be easily made from a 300 g batch. A photograph

of this glass is shown in Fig. 5 and some properties are given in Table 1. The water and acid durability data

indicate the glass has very good durability.

batch. The glass transition temperature depends on the

CdF2 content and it ranges from 290 to 330°C. These glasses have ultraviolet absorption edge at about 400

nm and no evident absorption is present in the visible region. They have IR transmittance higher than 70%

up to 7.5 pm and cutoff wavelength beyond 10 km (0.6 mm). Increasing the content of fluorine broadens

the transparent region in both visible and infrared regions.

References 4. Conclusions

New oxyfluoride glasses have been obtained in the

systems BizO,-PbO-ZnF, and B&O,-PbOCdF,. The glass forming region of the former is much smaller than that of the latter. The addition of ZnO to the latter

system significantly improves glass stability and a large size glass with composition 30Bi,O, * 2OPbO.

lOZn0 .40CdF2 can be easily obtained from a 300 g

[l] W.H. Dumbaugh, Phys. Chem. Glasses 19 (1978) 121.

[2] W.H. Dumbaugh, Phys. Chem. Glasses 27 (1986) 119.

[3] H.X. Zheng, P. Lin, R. Xu and J.D. Mackenzie, J. Appl. Phys.

68 ( 1990) 894.

[4] J.C. Lapp, J. Am. Ceram. Sot. 71 ( 1992) 1543.

[S] D.W. Hal1,M.A. Newhouse,N.F. Borrelli, W.H. Dumbaugh and

D.L. Weidman, Appl. Phys. Letters 54 (1989) 1293.

[6] M. Born and E. Wolf, eds., Principles of optics, 3rd Ed.

(Pergamon Press, London, 1965) p. 179.