Non-Ohmic and dielectric properties of CaCu3Ti4O12-MgO nanocomposites

Abstract

Graphical abstractDisplay Omitted Highlights? Addition of 5vol.% MgO can improve dielectric and nonlinear properties of CCTO. ? The low-frequency tan? of CCTO-MgO (5vol.%) was greatly reduced. ? e' of CCTO-MgO (5vol.%) is higher than 104 in the frequency range of 102-105Hz. ? Addition of 5vol.% MgO can enhance breakdown voltage and nonlinear coefficient. In this work, CaCu3Ti4O12-xMgO (x=0, 5, and 10vol.%) nanocomposites were prepared by a conventional mixed oxide method using CaCu3Ti4O12 and MgO nanopowders with particles sizes of about 100-300nm and 36-50nm, respectively. The dielectric and electrical properties of CaCu3Ti4O12 and CaCu3Ti4O12/MgO ceramics were investigated. The results revealed that addition of 5vol.% MgO can improve both dielectric and electrical nonlinear properties. The low-frequency loss tangent was greatly reduced; while, the dielectric constant was found to be higher than 104 in the frequency range of 102-105Hz. The decrease in a low-frequency loss tangent is caused by a decrease in DC conductivity. Addition of 5vol.% MgO can also enhance significantly the breakdown voltage and nonlinear coefficient of CaCu3Ti4O12 ceramic. Using impedance spectroscopy analysis, the increase in the breakdown voltage is attributed to an increase in the resistance of grain boundaries.