Crystallization of ZrSiO4 from a SiO2-ZrO2 Binary System: The Concomitant Effects of Heat Treatment Temperature and TiO2 Additions

The concomitant effects of adding varied amounts of TiO2 and temperature of heat treatment on the crystallization of ZrSiO4 from SiO2-ZrO2 binary systems were investigated. The results showed that the t-ZrO2 phase is stabilized in the amorphous SiO2 network, and the simultaneous occurrence of SiO2 crystallization along with the tetragonal zirconia (t-ZrO2) -> monoclinic zirconia (m-ZrO2) phase transition tends to activate the reaction between m-ZrO2 and SiO2 to yield ZrSiO4 at elevated temperatures. The formation of metastable ZrTiO4 is also witnessed in the intermediate temperatures that were dependent on TiO2 content, and its dissociation into their individual ZrO2 and TiO2 oxides resulted in ZrSiO4 formation. The Ti(4+)occupancy at the Zr4+ lattice sites ensured enhanced crystallization of ZrSiO4, and the limit of Ti4+ occupancy is determined as 9%. Excess TiO2 discarded from the ZrSiO4 lattice gets crystallized into rutile TiO2 (r-TiO2).