Enhanced dual-function capacitor–varistor properties in Bi2/3Cu3Ti4O12–AgNbO3 composite ceramics
Bi 2/3 Cu 3 Ti 4 O 12 (BCTO) ceramics combine dual functions, namely dielectric and nonlinear current and voltage properties. Reducing dielectric loss (tan δ ) and improving nonlinear coefficient ( α ) and breakdown field strength ( E b ) are prerequisites for the application of these materials. In this work, BCTO- x wt.%AgNbO 3 (BCTO- x AN, x = 0 − 0.1) ceramics were prepared via solid state method. All ceramics exhibited a single cubic perovskite structure. AN addition led to a decrease in grain size and improved the compactness of BCTO ceramics. Optical band gap showed a downward trend with the increase in AN amount while grain boundary resistance and conduction activation energy increased to a large extent. Therefore, there was a noticeable drop in tan δ while dielectric constants ( ε ′) of samples still remained above 10 4 . AN doping also enhanced barrier height and improved nonlinear characteristics of ceramics. Finally, BCTO-0.08AN composite ceramic possessed the most optimum dielectric and nonlinear properties ( ε ′ of ~ 1.13 × 10 4 , tan δ of ~ 0.031 at 10 kHz, α of ~ 5.75, and E b of ~ 8.5 kV/cm). These results reveal that BCTO- x AN ceramics have great application potential for capacitor–varistor dual-function devices.
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