Impedance and Raman spectroscopic studies of (Na_0.5Bi_0.5)TiO₃

Abstract

Polycrystalline powder of (Na0.5Bi0.5)TiO3 (NBT) was prepared by a high-temperature solid-state reaction route. Preliminary x-ray diffraction analysis carried out at room temperature showed the formation of a single phase compound with a rhombohedral crystal system. Scanning electron micrograph reveals the polycrystalline nature of the material with size anisotropy. Dielectric study showed an existence of diffuse phase transition around 300 °C. The ac conductivity spectrum obeyed the Jonscher power law. The temperature dependent pre-exponential factor (A) shows peak and frequency exponent (n) possesses a minimum at transition temperature. The bulk conductivity of the material indicates an Arrhenius type of thermally activated process with three different conduction mechanisms as different activation energies are observed. The hopping charge carriers dominate at low temperature, small polaron and oxygen vacancy dominates at intermediate temperature and ionic conduction at higher temperatures. Studies of impedance spectroscopy indicate that the dielectric relaxation is of non-Debye type. In situ high-temperature Raman spectroscopy shows discontinuous changes in the phonon frequencies across the rhombohedral–tetragonal transition. In addition, anomalous changes in the intensity and the linewidth of a lattice mode are found around 350 °C.

Investigation of the hydrothermal crystallisation of the perovskite solid solution NaCe1−La Ti2O6 and its defect chemistry

“…The spectra show broad bands consistent with other reports for NaLaTi 2 O 6 and for related perovskites such as Na 0.5 Bi 0.5 TiO 3 [42,46,[48][49][50]. This broadening may be due to the disorder on the A-site and the overlapping of multiple Raman modes.…”

Correlation of dielectric, electrical and magnetic properties near the magnetic phase transition temperature of cobalt zinc ferrite

“…The pre-exponential factor A(T) determines the strength of the polarizability. 34 The increase in the value of A(T) with increase in temperature establishes the increase in polarizability and hence dielectric…”

Tailoring of electrical properties of BiFeO3 by praseodymium

“…The increase in the value of ε r can be ascribed as the electron-phonon interaction [12]. The increase in ε r can be understood in terms of the thermally activated transport property and presence of space charges [13]. The dielectric anomaly (related to relaxation) is observed at 270 ℃ and it shifts towards higher temperature with increasing Pr substitution.…”

“…In another case, the motion of charge carriers is translational because of small value of n (<1). The value of n<1 signifies that the hopping motion involves a translational motion with a sudden hopping, whereas n>1 means that the motion involves localized hopping without the species leaving the neighborhood [13]. …”