低压ZnO压敏电阻的低温烧结及水基流延制备片式压敏电阻器的分析-微电子学与固体电子学专业论文.docx

华中科技大学博士学位论文 华 中 科 技 大 学 博 士 学 位 论 文 IV IV obviously increased. The effects of ZnO-B2O3 frit on the densification, phase transformation, microstructure and electrical properties of ZBTCM varistor ceramic were investigated. When ZnO-B2O3 frit is added to ZBTCM system, the sintering temperature only lowers 50℃. The grain growth kinetic exponent nZ and apparent activation energy QZ are calculated as 4.54 and 316.5 kJ/mol at the temperature below 1050°C due to the non-melting ZnO-B2O3 frit pining at ZnO grain boundaries, which inhibits the grain growth of ZBTCM varistor ceramic. However, nZ and QZ are 2.92 and 187 kJ/mol at the temperature higher than 1050°C due to the melting ZnO-B2O3 frit wetting the ZnO grain boundaries, which accelerates the grain growth of ZBTCM varistor ceramic. The ZnB2O4 phase, crystallized from ZnO-B2O3 frit, plays an important role in increasing the density of interface states and the barrier height. When ZnO-B2O3 frit content is equal to 0.1wt%, the varistor ceramics sintered at 1050℃ exhibit the best performance: E1mA=36.7V/mm, α=35.4, JL=0.35μA/cm2, △V1mA=12.1%, Whereas the △V1mA value is a little larger than 10%. The effects of Bi2O3-B2O3 frit on the densification, phase transformation, microstructure and electrical properties of ZBTCM varistor ceramic were investigated. When Bi2O3-B2O3 frit is added, the densification temperature could be reduces to 900℃. The grain growth kinetic exponent nB and apparent activation energy QB are 2.15 and 146.2 kJ/mol, which are much lower than that of ZnO-B2O3 frit doped varistor. It indicates that Bi2O3-B2O3 frit was more effective in improving the sintering properties of ZBTCM varistor ceramic than ZnO-B2O3 frit. The Bi4B2O9 phase, crystallized from Bi2O3-B2O3 frit, plays an important role in increasing the barrier height and nonlinearity of ZBTCM varistor ceramic. When Bi2O3-B2O3 frit content is equal to 2wt%, the varistor ceramics sintered at 900 ℃ exhibit the best performance: E1mA=124.9V/mm