Electrical properties of SrBi2(Nb0.5Ta0.5)2O9 ceramics

Aurivillius SrBi2(Nb0.5Ta0.5)2O9 (SBNT 50/50) ceramics were prepared using the conventional solid-state reaction method. Scanning electron microscopy was applied to investigate the grain structure. The XRD studies revealed an orthorhombic structure in the SBNT 50/50 with lattice parameters a=5.522 Å, b=5.511 Å and c=25.114 Å. The dielectric properties were determined by impedance spectroscopy measurements. A strong low frequency dielectric dispersion was found to exist in this material. Its occurrence was ascribed to the presence of ionized space charge carriers such as oxygen vacancies. The dielectric relaxation was defined on the basis of an equivalent circuit. The temperature dependence of various electrical properties was determined and discussed. The thermal activation energy for the grain electric conductivity was lower in the high temperature region (T>303.6 °C, Ea−ht=0.47 eV) and higher in the low temperature region (T<303.6 °C, Ea−lt=1.18 eV).