Influence of Cu Addition on the structure and dielectric of CaTiO3.pdf

Egypt. J. Sol., Vol. (25), No. (2), (2002) 175 Influence of Cu Addition on the Structure and Dielectric Properties of CaTiO3 M. Sh. Khalil and F. F. Hammad Inorganic Chemistry Department, National Research Center, Dokki, Cairo, Egypt The structure characterization and dielectric properties were studied for a series of copper-doped calcium titanates, Ca100-x Cux TiO3, where x =[Cu/(Cu+Ca)]% = 0.5, 1.0, 3.0 and 5.0, prepared by the conventional solid state reaction method. X-ray diffraction analyses indicate that all samples belong to the orthorhombic system. Cu addition results in non linear variation of lattice parameters. As the Cu concentration increases up to x ? 3.0, the lattice parameters (a, b and c) as well as the unit cell volume show an increase followed by a decrease with higher concentration of Cu (x 3). Variation of lattice parameters with Cu doping is discussed based on the relative ionic radius and the filling of the present vacancies. Variation of the dielectric constant (ε`) and dielectric loss (ε``) with frequency (100 -2x106 Hz) at different temperatures (300, 400, 500 and 600 K) was studied. It showed that pure CaTiO3 has the highest ε` value (1200) at low frequency. On the other hand, ε` and ε`` fall to lower values by the addition of CuO. By increasing the frequency up to 50 kHz, the measured ε` decreased for all the samples. At low frequencies, rapid increase of ε` and ε`` is observed with raising the temperature of measurements. At higher frequencies, the dielectric properties are independent on both the frequency and temperature. 1. Introduction: Oxides with the perovskite structure are well known for their ability to produce high dielectric constants with ferroelectric property leading to many important applications. Titanates as members of the perovskite structure family are widely used as ferroelectric materials with superior dielectric properties. The properties of these materials are lar