Dielectric relaxation and ac conductivity of WO3 added (Na1/2Bi1/2)TiO3 ceramic

Ceramic samples of WO3 added (Na1/2Bi1/2)TiO3 were prepared using a high-temperature solid-state reaction method. X-ray diffraction analyses indicate the formation of a single-phase orthorhombic structure. The apparent particle size and lattice strain are estimated using the Williamson-Hall plot. Dielectric studies revealed the relaxor behaviour and addition of WO3 shifted phase transition temperature as well as depolarization temperature of (Na1/2Bi1/2) TiO3 to higher side. ac impedance plots were used to analyse the electrical behaviour of samples in function of frequency at various temperatures. The ac impedance studies revealed the presence of the grain boundary effect and evidence of a negative temperature coefficient of resistance. Cole-Cole analysis indicated a non-Debye type dielectric relaxation. The ac conductivity obeys the universal power law. The pair approximation type correlated barrier hopping model explains the universal behaviour of the s exponent. The apparent activation energy of the conduction process and density of states at the Fermi level have been discussed.