Dielectric and impedance spectroscopy of Sr(Bi_0.5Ta_0.5)O₃ electroceramics

Polycrystalline sample of Sr(Bi_0.5Ta_0.5)O₃ was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction analysis confirms the formation of single-phase compound of orthorhombic crystal structure at room temperature. The study of microstructure of gold-coated pellet by scanning electron microscopy shows well-defined and homogeneous distribution of grains on the surface of the sample. The dielectric properties of the compound studied in a wide frequency range (1 kHz–1 MHz) at different temperatures (27–500 °C), exhibits that they are temperature dependent. Detailed analysis of impedance spectra showed that the electric properties of the material are strongly dependent on frequency and temperature. Studies of electric modulus show the presence of hopping conduction mechanism in the material with non-exponential type of relaxation. The decrease in value of bulk resistance on increasing temperature suggests the negative temperature co-efficient of resistance behavior of the material. The AC-conductivity spectrum provides a typical-signature of an ionic conducting system, and is found to obey Jonscher’s universal power law.