Structural, dielectric, and electrical characteristics of selenium-modified BiFeO_3-(BaSr)TiO_3 ceramics

摘要

The selenium (Se)-modified 0.5BiFeO_3-0.5(BaSr)TiO_3 was synthesized employing a high-temperature solid-state technique. Structural analysis (through Rietveld refinement) of the room-temperature X-ray diffraction pattern and data of the material confirms the tetragonal (P4mm) symmetry of the compound. Studies of scanning electron micrograph (SEM) and energy dispersive X-ray spectroscopy (EDS) data reveal the nature and characteristics (i.e., size, shape and distribution of grains, grain boundaries, voids and presence of elements, etc.,) of surface morphology and structure of the compound. Detailed analysis of temperature and frequency dependence of dielectric and impedance data exhibits the relaxor type of ferroelectric behavior and semiconductor (negative temperature coefficient of resistance) nature of the material. The material is found to have high resistivity and low dielectric (tangent) loss. Study of the temperature dependence of leakage current characteristics (i.e., electric field dependent current density) shows the leaky behavior of the material. The Se-modified 0.5BiFeO_3-0.5(BaSr) TiO_3 (BFBST), compared to its components (BFBST and pure BiFeO_3), material possesses different types of conduction process, like space charge limited (SCLC), Ohmic, Hopping type. Poole-Frenkel emission (PFE) and Schottky emission (SE) fitted data give an evidence/idea about the bulk-limited and interface-limited conduction mechanism present in the system. The energy gap values (E_g) of Se substituted BFBST and BiFeO_3 are found to be 0.55 eV and 0.78 eV, respectively, in the low-temperature range.