Ferroelectric phase transition in Ni-doped lead molybdate ceramics

Abstract

The effects of Ni2+ doping on structural, microstructural, dielectric and electrical properties of lead molybdate PbMoO3 have been investigated. Polycrystalline samples of Ni-doped lead molybdate Pb(Ni1/2Mo1/2)O3(PNM) were synthesized by a solid-state reaction technique. Structural and microstructural properties of the compound were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. From the X-ray diffraction study it is found that the compound has an orthorhombic crystal structure at room temperature. The SEM micrographs of the compound show uniform distribution of grains throughout the surface of the compound. Detailed studies of dielectric constant, loss, impedance and conductivity both as a function of frequency and temperature suggest that the compound undergoes a diffuse phase transition (DPT) at 136°C. The impedance analysis (Cole-Cole plot) of the compound shows that the compound has bulk conduction at low temperature. The electrical properties show that the compound has negative temperature coefficients of resistance (NTCR) and ionic conduction. The conductivity (ac and dc) studies of the compound suggest that the conductivity of the compound increases with increasing frequency. The energy gap (Eg) of the compound was calculated from the plot of dc resistivity versus temperature and was found to be 0.77 eV at high temperature.