The effect of sintering temperature on the microstructure, electrical and dielectric properties of (V, Mn, Co, Dy, Bi)- codoped zinc oxide ceramics was investigated in this study. An increase in the sintering temperature increased the average grain size from 4.7 to 10.4 μm and decreased the sintered density from 5.47 to 5.37 g/cm3. As the sintering temperature increased, the breakdown field decreased greatly from 6027 to 1659 V/cm. The ceramics sintered at 900 oC were characterized by the highest nonlinear coefficient (36.2) and the lowest low leakage current density (36.4 μA/cm2). When the sintering temperature increased, the donor concentration of the semiconducting grain increased from 2.49 × 1017 to 6.16 × 1017/cm3, and the density of interface state increased from 1.34 × 1012 to 1.99 × 1012/cm2. The dielectric constant increased greatly from 412.3 to 1234.8 with increasing sintering temperature.

Thermoelectric power, dc conductivity, and the dielectric relaxation properties of La2NiO4.03 are reported in the temperature range of 77 K - 300 K and in a frequency range of 20 Hz - 1 MHz. Thermoelectric power was positive below 300K. The measured thermoelectric power of La2NiO4.03 decreased linearly with temperature. The dc conductivity showed a temperature variation consistent with the variable range hopping mechanism at low temperatures and the adiabatic polaron hopping mechanism at high temperatures. The low temperature dc conductivity mechanism in La2NiO4.03 was analyzed using Mott's approach. The temperature dependence of thermoelectric power and dc conductivity suggests that the charge carriers responsible for conduction are strongly localized. The relaxation mechanism has been discussed in the frame of the electric modulus and loss spectra. The scaling behavior of the modulus and loss tangent suggests that the relaxation describes the same mechanism at various temperatures. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy of ~ 0.106eV. At low temperature, variable range hopping and large dielectric relaxation behavior for La2NiO4.03 are consistent with the polaronic nature of the charge carriers.