Effect of Al2O3, MgO and SiO2 additives on electrical resistivity and sintering property of ZnO ceramics

The effect of metal oxide additives; Al2O3, MgO and SiO2 to ZnO ceramics was investigated from the point of view of both the electrical resistivity and the sintering property. Doping of Al2O3 to ZnO ceramics with 5.0-20.0 mol% caused on increase of the electrical resistivity with increasing the concentration of Al2O3, but also caused deterioration of density after sintering. Temperature coefficient of resistivity of ZnO ceramics doped with over 5.0 mol% MgO changed from a negative to a positive value. Sintering density of ZnO ceramics was improved by small doping of SiO2. ZnO ceramics including above 3 kinds of additives: Al2O3, MgO and SiO2 with suitable controlled concentration respectively, showed good electrical performance (resistivity, linearity, temperature coefficient) as a linear resistor. The microstructure of this ZnO ceramics were mainly formed by ZnO, Zn-Al-O complex oxides and pores.