Enhanced Breakdown Field of xSrCu3Ti4O12/(1-x)CaCu3Ti4O12 Composite Ceramics

xSrCu(3)Ti(4)O(12)/(1-x)CaCu3Ti4O12 (x=0.2, 0.4, 0.6, 0.8)composite ceramics were prepared by traditional solid-state method with sintering for 5 h at 1000 degrees C. Breakdown fields of all the samples were greatly enhanced compared to CCTO ceramics, especially for samples of 0.4SrCu(3)Ti(4)O(12)/0.6CaCu(3)Ti(4)O(12) and 0.6SrCu(3)Ti(4)O(12)/0.4CaCu(3)Ti(4)O(12). SEM images displayed that round shape grains with size of 1 mu m were extensively existed in samples. Statistic of grain size distribution from SEM images proved that longer sintering time lead to larger average grain size. I-V measurement indicated that breakdown voltages of samples in both sintering conditions were highest when x=0.4 and lowest when x=0.8, in which highest value of breakdown voltages is 25 kV.cm(-1) for 0.4SrCu(3)Ti(4)O(12)/0.6CaCu(3)Ti(4)O(12). In addition, it was found from C-V measurements that reduced donor density was responsible for the elevated barrier height while interface density remained almost constant.