Study on dielectric properties of lanthanum copper tantalate ceramics by impedance spectroscopy

A new perovskite ceramic material with the composition La2/3CuTa4O12 was synthesized by solid state reaction method. SEM observations revealed dense and fine-grained microstructure and not uniform grain size distribution in the ceramics sintered in the temperature range 1180-1220 degrees C. Impedance spectroscopy studies were carried out in the temperature range from 55 to 700 degrees C at frequencies 10 Hz-2 MHz. Three types of dielectric responses were recognized, attributed to grains, grain boundaries and the electrode-sample interface. The relaxation times determined from the impedance data follow the Arrhenius law with the activation energies of 025 eV and 0.94 eV for grains and grain boundaries, respectively. DC electrical conductivity of the investigated ceramics was investigated in the temperature range 20-700 degrees C The determined activation energy of electrical conduction was about 0.5 eV. The dielectric properties of La2/3CuTa4O12 ceramics were compared with those of other A(2/3)CuTa(4)O(12) (A=Y, Nd, Sm, Gd, Dy, Bi) materials, being the spontaneously formed internal barrier layer capacitors, and some essential differences were found. (C) 2014 Elsevier Ltd. All rights reserved.