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ZrO₂ (Zirconium Dioxide)

Family	Opacifier
Weight	123.220

COLE - Co-efficient of Linear Expansion	0.020
MLPT - Melting Point (MP)	2900C (From The Oxide Handbook)

Notes

Zirconium oxide is extremely refractory. It is primarily used as an opacifier in glazes, it does not go into solution in the glaze and so does not participate in the chemistry (see notes on Zircon about its opacification).

It is beneficial to add zircon to transparent glazes in amounts up to 3% to improve hardness and reduce thermal expansion. This is because small amounts can be taken into solution and will therefore not opacify.

ZrO2 reduces the thermal expansion of a glaze (although not by the same mechanism as other oxides that impose their expansion by going into solution in the glaze melt).

ZrO2 reduces glaze melt fluidity.

Mechanisms

Glaze Opacifier - White
Zirconium is an effective opacifier, especially in the Zirconium Silicate form. Materials of finer particle size are more effective. In lead glazes a cream tint is likely. Glazes high in boron or alkalis, or low in alumina and silica may not opacify well.

Out Bound Links

(Materials - Material source) Zircon - ZrO2.SiO2
Zirconium Silicate
(Oxides - Related) ZrO - Zirconium Oxide, Zirconia

Pictures
Flow tester demonstrates how zircon opacifys and stiffens a glaze melt

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Digitalfire Ceramic Oxides Directory

ZrO2 (Zirconium Dioxide)

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ZrO₂ (Zirconium Dioxide)