| At1980s, the linearization of ZnO ceramic from ZnO basedvaristor has successfully developed by Japan. The ZnO-based linearresistance ceramics have been widely used in electronic-power sectorby their low cost and perfect electronic properties. With the needs ofEHV power transmission circuit and electronic componentminiaturization, fabrication of ZnO-based linear resistance ceramics hasbecome a research foucs at present. This paper discussed the influencerules of preparation process and the basic formula on the electronicproperties and microstructure of ZnO-based linear resistance ceramics.This paper firstly investigated influence rules of the addition ofadditive such as A12O3, TiO2, MgO and little rare earth oxide on themicrostructure and electronic properties of ZnO-based linear ceramics.The characterization of this material was by XRD, SEM, EDS and theelectronic performance test; the results demonstrated that the additionof A12O3has a significant effect on the resistivity and nonlinearcoefficient of the ZnO ceramics. The doping of the A12O3can not onlychange the generation amount of second phase and the particle size ofmatrix, but also can reduce the grain boundary barrier. When thecontent of A12O3addition was9wt%, the nonlinear coefficient andresistivity were1.17and285.24·cm, respectively. The doping of TiO2can imporve the compactness and uniformity of the products`matrix. Soit has an obviously effection on the energy density of ZnO linearceramics, When the addition content of TiO2was7wt%, the energydensity was780J/cm3. The addition of MgO has a significant effect onthe resistance-temperature coefficient of the ZnO ceramics, when theMgO was7wt%, resistance-temperature coefficient reached3.4×10-4/℃,and the energy density and nonlinear coefficient were812J/cm3and1.12, respectively. At the same time, with the doping of La2O3and Y2O3,it can greatly imporve the uniformity of matrix particles. When the addition amount of La2O3and Y2O3were0.5mol%and0.25mol%, thenonlinear coefficient were1.12and1.14, energy density were812J/cm3and809J/cm3, resistance-temperature coefficient were3.4×10-4/℃and2.7×10-4/℃, respectively.Subsequently, this paper discussed the preparation process, whichinfluenced the microstructure and electrical properties of ZnO linearceramic. The results showed that calcining additives can imporve theactivity of powders, and futher imporve the microstructure of thesample, so as to increase the comprehensive eletronic performanceparameters. When calcined raw powders at1100℃for2times, theresistivity was792·cm, resistance-temperature coefficient was3.94×10-4/℃, stability of resistivity was56.4%, nonlinear coefficientand energy density were1.10and821J/cm3, respectively.The samples`microstructure and electrical properties can effectgreatly by the suitable sintering temperature and cooling rate. Theanalysis of comprehensive test revealed the best sintering temperaturerange was13201360℃, cooling rate was around100℃/h. and whenthe sintering temperature and cooling rate were1340℃and100℃/h,the resisitivity was790·cm, resistance-temperature coefficient was4.04×10-4/℃, nonlinear coefficient was1.10, energy density was821J/cm3, stability of resistivity was57.4%.Finally, based on the former research and techniques foundation,adjusting the additive formula and doping different amount NiO werestudied in detail. Then discuss the affection of different NiO doping onthe microstructure and electronic properties of ZnO linear resistivityceramic. This study using nominal compositions of73.79ZnO-3.0MgO-2.0La2O3-9.0A12O3-1.0SiO2-11.21（15mol%） NiO,and mixed the NiO, ZnO powders to calcine, then employing the bestpreparation precess to produce ZnO linear ceramic. The samples`resisitivity was301.25·cm, resistance temperature coefficient was3.14×10-4/℃, nonlinear coefficient was1.13, energy density andstability of resistivity were802J/cm3and57.4%, respectively. |
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