Dielectric and varistor properties of rare-earth-doped ZnO and CaCu₃Ti₄O₁₂ composite ceramics

Abstract

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb -and- Co doped ZnO and TiO 2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol–gel methods respectively, and then obtained the TCCTO/ ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of ~210(1 kHz) with a nonlinear coefficient of ~11. The dielectric behavior of TCCTO/ ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

Superior dielectric and varistor properties of ZnO or SnO2 diffused calcium copper titanate ceramics

“…It is known from the literature that the dielectric and varistor properties of CCTO ceramics were studied, which were fabricated either by combining CCTO with ZnO or SnO 2 (henceforth, represented as ZnO/SnO 2 ) or doping with ZnO/SnO 2 . 26,27 In both the cases, it was observed that there was an improvement in either the dielectric properties or varistor characteristics but not the both, suggesting that this approach of either doping or making composites with ZnO/SnO 2 is not an encouraging strategy. Therefore, we thought that it would be worthwhile to investigate into the effects of placing these oxides at the grain boundaries of CCTO ceramics using a very primitive/facile method on their physical (dielectric and varistor) properties.…”

Microstructure and nonohmic properties of SnO2–Ta2O5–TiO2 varistor system doped with CuO

“…The varistor voltage (V B ) was determined at 1 mA/cm 2 (Ref. 21) and the leakage current (I L ) was the current density at 0.75V B . Moreover, the nonlinear coefficient (α) was obtained by the following equation:…”