The structural and electric properties of the perovskite system BaTiO3-Ba(Fe1/2Ta1/2)O-3

摘要

Compounds in the pseudo-binary BaTiO3-Ba(Fe1/2Ta1/2)O-3 system have been synthesized at 1500degreesC in air and characterized by X-ray and electron diffraction as well as impedance analysis and Mossbauer spectroscopy. The symmetry of Ba(Fe1/2Ta1/2)O-3 is found to be trigonal with the space group P3m1. Two solid solutions exist in the BaTi1-xFex/1Tax/1O3 system at room temperature. The first (SS1) is in the composition range 0 less than or equal to x less than or equal to 0.07 and is tetragonal, P4mm, while the second broader solid solution, (SS2) 0.12 less than or equal to x less than or equal to 1, is trigonal and has the space group P3ml. The conductivity becomes higher with reduced amount of Ti in the structure. The activation energy of conductivity differs between the two solid solutions, 0.80eV for SS1 and 0.30eV for SS2, which indicates different mechanisms. The maximum of the real part of the pemittivity recorded for compounds in SS1 decreases towards room temperature with increasing amount of Fe/Ta doping and a high dielectric constant of around 7000 is found for BaTi(0.94)Fc(0.03)Ta(0.03)O(3). (C) 2004 Elsevier Inc. All rights reserved.