Crystal Phases of Nonohmic Zinc Oxide Ceramics

概要

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The crystal phases of nonohmic ZnO ceramics, having Bi_2O_3, Sb_2O_3, Co_2O_3, MnO_2 and Cr_2O_3 as additives, have been investigated by classifying and clarifying them as a function of the amounts of the additives and sintering temperature, and synthesizing their single phases. These ceramics consist of ZnO phase dissolving Co and Mn components, spinel phase of Zn_7Sb_2O_<12> dissolving Co, Mn and Cr components, and Bi-rich phases (B, C, D or B´). The B-phase is a δ-Bi_2O_3 type phase (a=5.59Å) having a fundamental composition of 12Bi_2O_3・Cr_2O_3. The C-phase is a tetragonal phase (a=7.76Å, c=5.75Å) having a fundamental composition of 14Bi_2O_3・Cr_2O_3. The D-phase is a β-Bi_2O_3 type tetragonal phase (a=10.93Å, c=5.62Å) dissolving a large amount of Zn component and a small amount of Sb component. The B´-phase is also a δ-Bi_2O_3 type phase (a=5.48Å) formed in the system Bi_2O_3-ZnO-Sb_2O_3. A solid solution between B and B´is formed. The nonohmic property of ZnO ceramics is improved with the changes of phases, B→C→D or D+B´, by raising the sintering temperature. The extinction of the nonohmic property caused by the change in the amounts of additives and sintering temperature corresponds to that of ZnO or Bi-rich phases in the ceramics.
社団法人応用物理学会の論文
1978-01-05