GRAIN-GROWTH OF ZINC-OXIDE DURING THE SINTERING OF ZINC-OXIDE ANTIMONY OXIDE CERAMICS

Grain growth in a high-purity ZnO with systematic additions of Sb2O3 from 0.29 to 2.38 wt% was studied for sintering in air from 1106-degrees to 1400-degrees-C. The results are discussed and compared with previous studies of pure ZnO and ZnO with Bi2O3 additions in terms of the kinetic grain growth expression: G(n) - G0n = K0t exp(- Q/RT). Additions of Sb2O3 inhibited the grain growth of ZnO and increased the grain growth exponent (n-value) to 6 from 3 for pure ZnO and 5 for the ZnO-Bi2O3 ceramic. The apparent activation energy for the grain growth of ZnO also increased to about 600 kJ/mol from 220 kJ/mol for pure ZnO and 150 kJ/mol for the ZnO-Bi2O3 ceramics. Both the grain growth exponent and the activation energy were independent of the Sb2O3 content. Particles of the Zn7Sb2O12 spinel were observed on the grain boundaries and at the grain triple point junctions. It was also observed that the Sb2O3 additions caused twin formation in each ZnO grain. It is concluded that both the Zn7Sb2O12 particles and the twins are responsible for the ZnO grain growth inhibition by Sb2O3.