Optimized dual-function varistor-capacitor ceramics of core-shell structured xBi(2/3)Cu(3)Ti(4)O(12)/(1-x)CaCu3Ti4O12 composites

摘要

xBi(2/3)Cu(3)Ti(4)O(12)/(1-x)CaCu3Ti4O12 composites were prepared by traditional solid-state reaction method. Extremely high nonlinear coefficient of 25 and breakdown field of 18.92 kV.cm(-1) were obtained in small current range of 0.1 - 1 mA.cm(2). In addition, reduced dielectric loss of 0.055 was achieved with high dielectric constant of 1369. Optimized nonlinear and dielectric properties were integrated to make the composites a promising dual-function varistor-capacitor candidate. Microstructure analysis discovered two areas with various Bi/Ca ratio, designated as Bi-H and Bi-L respectively. It was found that the maximum ratio of Bi-H/Bi-L heterogeneous interface corresponded to optimized nonlinear and dielectric performance, which was associated with elevated potential barrier height and huge grain boundary resistance. Combined with relaxation analysis, a core-shell structure was proposed to elaborate microstructure evolution in xBi(2/3)Cu(3)Ti(4)O(12)/(1-x)CaCu3Ti4O12 composite. According to the core-shell model, variation of heterogeneous interface was illustrated on how to influence nonlinear properties, which was well fitted to experimental results.