CRISTOBALITE GROWTH INHIBITOR IN PYREX BOROSILICATE GLASS GALLIUM OXIDE

The effect of gallium oxide on cristobalite formation in Pyrex borosil icate glass has been studied. XRD results show that with 20 vol. % gal lium oxide, the precipitation of cristobalite at 800-degrees-C is comp letely prevented. This result is further evidenced by the linear therm al expansion measurement, in which, in contrast to the system without a sufficient amount of gallium oxide (0-10 vol. %), the thermal expans ion coefficient of the composite with 20 vol. % gallium oxide remains unchanged with sintering time at the temperature investigated and, mor eover, is very close to the theoretically calculated value.