Grain growth in TiO2-added ZnO–Bi2O3–CoO–MnO ceramics prepared by chemical processing

The effect of TiO2 on the grain growth of the ZnO–Bi2O3–CoO–MnO ceramic system prepared by chemical coprecipitation, was studied between 1150 and 1300 °C in air. Bi2O3 melts during firing, and then TiO2 dissolves into Bi2O3-rich liquid. TiO2 initially reacts with Bi2O3 to form Bi4Ti3O12. Above ≈1050 °C, Bi4Ti3O12 reacts with ZnO to form Zn2TiO4 spinel phase. The kinetic study of grain growth carried out using the expression Gn–Gon=Ko·t·exp(−QRT) gave grain exponent (n) value as 6 and the apparent activation energy (Q) as 226.46 kJ/mol. 1.00 mol% TiO2 addition increased the grain growth exponent value from 6 to 7 and apparent activation energy with 1.00 mol% TiO2 addition was found to be 197.10 kJ/mol. The ZnO grain size gradually increases with increasing TiO2 content. Addition of TiO2 may increase the reactivity of the Bi2O3-rich liquid towards the ZnO grain, thus affecting the ZnO grain growth.