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Viscosity Temperature Dependence and Crystallization of Heavy Metal Fluoride Classes

Published online by Cambridge University Press:  25 February 2011

S. N. CrichtoN ,
R. Mossadegh ,
C. T. Moynihan ,
P. K. Gupta  and
M. G. Drexhage
S. N. CrichtoN
Affiliation:
Rennselaer Polytechnic Institute, Troy, NY 12180
R. Mossadegh
Affiliation:
Rennselaer Polytechnic Institute, Troy, NY 12180
C. T. Moynihan
Affiliation:
Rennselaer Polytechnic Institute, Troy, NY 12180
P. K. Gupta
Affiliation:
Ohio State University, Columbus, OH 43230
M. G. Drexhage
Affiliation:
Rome Air Development Center, Hanscom AFB, MA 01731
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Abstract

The temperature dependence of the viscosity of heavy metal fluoride glasses is important for determining processing temperatures for procedures such as fiber drawing and in understanding crystallization behavior in these systems. Viscosity data in the glass transition region and in the liquid region have been measured by several different laboratories for ZBLA (58 ZrF4-33 BaF2-5 LaF3-4 AlF3) and ZBLAN viscosity-temperature curves for these two compositions are highly non-Arrhenius in nature, and cannot be described by the Fulcher equation; however the Cohen-Crest equation fits the data very well. On a reduced temperature scale (Tg/T), the viscosity curves nearly coincide, suggesting the possibility of a master viscosity equation for fluorozicronate glasses. Crystallization temperatures for these compositions have been measured by differential scanning calorimetry. On reheating, the first crystallization product for both compositions is a barium fluorozicronate phase. However, ZBLAN glass does not crystallize until a much lower viscosity is reached, compared to ZBLA. These results indicate that the devitrification behavior for ZBLAN is due to additional entropy of mixing from the addition of NaF.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 88: Symposium P – Optical Fiber Materials and Properties , 1986 , 115
Copyright
Copyright © Materials Research Society 1987

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References

REFERENCES

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