Influence of Cu Addition on the Structure and Dielectric Properties of CaTiO3

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.