Modification of the dual-function varistor-capacitor properties of Bi2/3Cu3Ti4O12 ceramic by doping with Sr0.99La0.01TiO3

Abstract

Bi2/3Cu3Ti4O12 (BCTO) ceramic materials can be used as varistor-capacitor dual-function devices. In this research, Bi2/3Cu3Ti4O12-xwt%Sr0.99La0.01TiO3 (BCTO-xSLT) ceramic composites were prepared using the solid-state method. The microstructure, phase composition, and morphology along with the optical, dielectric, and nonlinear properties of ceramics were systematically investigated. All the samples exhibited the cubic perovskite structure. Notably, the grain size of BCTO decreased while its compactness increased at a small amount of incorporated SLT. Moreover, the SLT addition significantly decreased the dielectric loss (tanδ) with a prominent increase in the optical band gap (Eg) of ceramics. Interestingly, the dielectric constant (ε′) of the composites remained greater than 103, whereas the enhanced frequency and temperature stability as well as the nonlinear performance was observed as well. Among the various compositions, the sample with x = 0.06 showed the optimum dielectric and nonlinear properties with appreciably high ε′ of ∼11322, the lowest tanδ of ∼0.026 at 10 kHz, the highest nonlinear coefficient (α) of ∼7.49, the largest breakdown field strength (Eb) of ∼10.45 kV/cm, and the greatest energy storage density (w) of ∼54.2 mJ/cm3. These improved optical, dielectric, and nonlinear properties of the BCTO-SLT composites were attributed to the enhanced geometric (grain boundary number and compactness) and intrinsic (Eg, grain boundary resistance, and barrier height) properties of the grain boundary. The study demonstrates that BCTO-SLT ceramics can be potential candidates for capacitor-varistor dual-function devices.