Effect of ZnAl2O4 content on the microstructure and electrical properties of ZnO-based compound conductive ceramics

ZnO-ZnAl2O4-SiO2-Y2O3-MgO conductive ceramics were fabricated with different amount of ZnAl2O4 content. The effects of ZnAl2O4 on the microstructures and electrical properties of ZnO-based compound conductive ceramics were investigated. Results showed that the continuously adjustable resistivity could be obtained under the percolation threshold through increasing ZnAl2O4 content and improving the preparing technology. It was found that ZnAl2O4 grain would be encased in the major ZnO grains, with less than 5.0 mol%. When more ZnAl2O4 doping in the samples, it acted as a barrier blocking ZnO grain growth. Interestingly, the dielectric properties indicate that the Maxwell-Wagner interfacial polarization and the threshold effect exists in the matrixes. At the same time, the resistance-temperature (R-T) characteristics verify that the conduction mechanism of ZnO-based conductive compound ceramics is a thermally activated progress and the grain-boundary effect is negligible. The improvement of the microstructures and electrical properties has a potential application in the high frequency electrical fields.