Dielectric and electrical properties of La_xSr_1-3x/2Cu₃Ti₄O₁₂ ceramics

The Electrical properties and dielectric characteristics of La_xSr_1-3x/2Cu₃Ti₄O₁₂ (x:=0.00, 0.01, 0.02, 0.04, 0.05) ceramics using conventional solid-state reaction method were investigated in details. It is noticeable that the breakdown field was significantly enhanced to 15.8kV/cm when x:=0.01. The enhancement in breakdown field was ascribed to the grain boundary resistance strengthened by rare-earth La. In addition, four relaxation peaks were found in modulus spectra except La_0.01Sr_0.985Cu₃Ti₄O₁₂ which showed only three relaxation peaks related to the first and second ionization of oxygen vacancy and dc conduction. The addition of 1% La slightly increased activation energy related to the second ionization of oxygen vacancy. Moreover, the rare-earth doping slightly depressed the activation energy on dc conductivity indicating the decrease of the height of Schottky barrier resulting in the reduction of nonlinear coefficient. The depression of Peak 4 in La_0.01Sr_0.985Cu₃Ti₄O₁₂ indicated that La played an important role in depressing a newly found intrinsic defect. The intrinsic defect with activation energy of 0.45eV in SrCu₃Ti₄O₁₂ may be originated from the second ionization of Cu vacancy and was even easier to be generated with more than 1% La added to SrCu₃Ti₄O₁₂.