Electrical and dielectric behaviour of Na_0.5La_0.25Sm_0.25Cu₃Ti₄O₁₂ ceramics investigated by impedance and modulus spectroscopy

Polycrystalline samples of Na0.5La0.25Sm0.25Cu3Ti4O12 ceramics were prepared by solid state sintering. Its crystallographic structure, electrical properties and dielectric behaviour are investigated over wide ranges of temperature (30–325 °C) and frequency (42 Hz–1 MHz). Rietveld refinement of the powder diffraction data has confirmed a cubic, single phase structure with space group Im3. This ceramic material exhibits colossal value of dielectric constant with very low values of loss factor, over wide frequency ranges and thus highlights the quality of the sample to be used for the fabrication of capacitive devices. Impedance spectroscopic studies have revealed that the compound is electrically heterogeneous. The scaling behaviour of Z″ suggests a temperature independent distribution of relaxation time. The mismatch in the peak frequencies of Z″/Zmax″ and M″/Mmax″ suggest that the relaxation mechanism is dominated by short range movement of charge carriers.