Phase transition and electrical properties of strontium orthovanadate

The current research work reports the study of phase transition and transport mechanism in lead-free strontium orthovanadate (Sr3V2O8), prepared using a high-temperature solid-state reaction technique. Preliminary X-rays diffraction studies exhibit the formation of a single-phase compound in the trigonal crystal system. Study of microstructure of gold-coated pellet by scanning electron microscopy (SEM) shows well-defined and homogeneous grains in the morphology. Detailed studies of dielectric parameters (epsilon(r) and tan delta) of the compound as a function of temperature at some selected frequencies reveal their independence for a wide range of temperatures. An anomaly in relative permittivity (epsilon(r)) suggests the existence of a ferroelectric-paraelectric phase transition of diffuse-type in the material that confirms through the detailed studies of its electric polarization. Detailed studies of impedance and related parameters exhibit that the electrical properties of the material are strongly dependent on temperature, and bear a good correlation with its microstructure (i.e., bulk, grain boundary, etc.). The decrease in value of bulk resistance on increasing temperature suggests the negative temperature co-efficient of resistance (NTCR) behavior of the material. Studies of electric modulus indicate the presence of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius and NTCR type of behavior in the material. The ac conductivity spectrum shows a typical-signature of an ionic conducting system, and is found to obey Jonscher's universal power law. (C) 2013 Elsevier B.V. All rights reserved.