ZnOとZnO-Bi_2O_3セラミックスの結晶粒成長

概要

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Grain growth in a high purity ZnO and for the same ZnO with Bi_2O_3 additions from 0.5 wt% to 4 wt% was studied for sintering from 900℃ to 1400℃ in air. The results are discussed and compared with previous studies in terms of the phenomenological kinetic grain growth expresson; G^n-G^n_0=K_0t exp(-Q/RT). For the pure ZnO, the grain growth exponent or n - value was observed to be three while the apparent activation energy was 224 ± 16 kJ/mol. These parameters substantiate the Gupta and Coble conclusion of a Zn^<2+> lattice diffusion mechanism. Additions of Bi_2O_3 to promote liquid phase sintering increased ZnO grain size and the grain growth exponent to about five, but reduced the apparent activation energy to about 150 kJ/mol, independent of Bi_2O_3 content. The preexponential term K_0 was also independent of Bi_2O_3 content. It is concluded that the grain growth of ZnO in liquid - phase - sintered ZnO - Bi_2O_3 ceramics is controlled by the phase boundary reaction of the solid ZnO grains and the Bi_2O_3 rich liquid phase.
1989-09-30