Impedance and modulus spectroscopic studies of lead free Na12 Dy12 TiO3 Ceramic

Abstract

A lead-free perovskite ceramic, Na12Dy12TiO3 (NDT), was synthesized via the conventional solid state reaction method. The sample’s structural, microstructural, and electrical characterizations were performed over the varying range of frequency and temperature. The detailed electrical behavior of the samples has been analyzed and explored by applying impedance spectroscopy. The structural study confirmed the orthorhombic structure of NDT material, with the presence of a very small contribution of the impure pyrochlore phase. The dielectric permittivity of the sample as a function of temperature shows the ferroelectric to paraelectric phase transition temperature to be ∼94 °C, and the shift of phase transition temperature is attributed to its structure. The frequency and temperature-dependent electrical features are studied within the framework of impedance, modulus, and conductivity spectra. The Nyquist plots detect the contribution of grain/grain boundaries to the inclusive polarizations. The presence of two depressed semicircular arcs in the Nyquist Plots (both grain/grain boundaries contribute to electrical properties) was approached for higher temperatures (≥350 °C), suggesting the relaxation phenomena to be temperature dependent with a distribution of relaxation times. Also, the modulus spectra analysis confirms the temperature-dependent multiple relaxation phenomena to be of the Non-Debye type and is present in the sample at ≥350 °C. The conductivity spectra confirm the presence of dc conduction at ≥350 °C and a temperature-dependent polaron hoping conduction behavior with the validity of Johnscher’s universal law.

Keywords

• Ceramics
• Polarons
• Impedance Spectra
• Modulus Spectra
• Conductivity spectra
• Phase transition