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

Abstract

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 degreesC in air. Bi2O3 melts during firing, and then TiO2 dissolves into Bi2O3-rich liquid. TiO2 initially reacts with Bi2O3 to form Bi4Ti3O12. Above approximate to1050 degreesC, Bi4Ti3O12 reacts with ZnO to form Zn2TiO4 spinel phase. The kinetic study of grain growth carried out using the expression G(n)-G(o)(n) = K(o)(.)t(.)exp(-Q/T) 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. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.