Refractory Technology
Zirconia refractories are not used in

Lining high temperature ceramic kilns
High frequency induction furnaces in the form of inductors
Furnaces subjected to fluctuating temperature
Making sheaths for thermocouple

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Refractory Technology
Natural silica

All of these
Is not stable at high temperature
Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes
Mainly contains quartz

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