1. Introduction
Glazed ceramic tiles are the most common building material
for floor and wall covering. Glazes are produced from frits.
Frit is a ceramic composition that has been melted in a special
melting oven, quenched to form a granulated glass. Frits form
an important part of the batches used in enamels and ceramic
glazes formulations.
Among the available commercial frits, those containing zircon
(ZrSiO4) and zirconia (ZrO2) are of great interest. ZrSiO4
gives rise to opaque frits, which are commonly called “zirconium
whites”. This type of frits, which is glossy and opaque,
contains high amount of zircon because it improves the chemical
properties and the degree of opacity. Zircon and zirconia can
be added to the glaze as a mill addition or included as zirconia