Microstructural evolution during sintering of Bi2O3-doped ZnO

The electrical properties of a ceramic varistor depend strongly on its microstructural uniformity. In the present study, the microstructure of the Bi2O3-doped ZnO after sintering is characterized. A very small amount, 0.04 mol%, of Bi2O3-addition may induce density inhomogeneity in the early stage of sintering. A critical amount, >0.09 mol%, of Bi2O3 is needed to result in density uniformity. The addition of Bi2O3 can enhance the coarsening rate of ZnO grains; nevertheless, the grain size distribution is not affected.