Microstructure development in low-antimony oxide-doped zinc oxide ceramics

The grain growth of ZnO ceramics sintered with low additions of Sb2O3 (< 500 ppm of Sb) was investigated. Additions of Sb < 250 ppm resulted in a coarse-grained microstructure with large ZnO grains (55-70 mu m), much larger than the grain size of ZnO ceramics without any Sb2O3 addition (45 mu m). The addition of 500 ppm of Sb resulted in a fine-grained microstructure with an average ZnO grain size of about 12 mu m. The results are explained by an inversion-boundary (IB) -induced grain-growth mechanism. The grain-growth exponent has a value of about 2 as long as the grains containing IBs grow at the expense of IB-free grains. It increases to about 4 after the IB-containing grains impinge on each other, and achieves values above 10 for additions of 500 ppm of Sb when IBs nucleate in nearly all the ZnO grains so that grains with IBs prevail in the microstructure at an early stage in the grain-growth process.