Structural, thermal and dielectric properties of La_(3/2)Bi_(3/2)Fe_5O_(12)

摘要

Polycrystalline La_(3/2)Bi_(3/2)Fe_5O_(12) (LBIO) compound was prepared by a conventional high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) analysis confirms the formation of single-phase compound in an orthorhombic crystal system at room temperature. The elemental content of the compound has been analysed by EDS microanalysis. Microstructural analysis by scanning electron microscopy (SEM) shows that the compound has well defined grains, which are distributed uniformly throughout the surface. Studies of temperature variation of dielectric response at various frequencies show multiple dielectric anomalies at 200 and 370℃. It is interesting to note that the loss tangent (tan δ) seems to be reduced at higher frequencies after reaching the instrumental saturation. Also, a couple of weak endothermic peaks were observed in differential thermal analysis (DTA) corresponding to 200 and 370℃ phase transition temperature. As soon as the phase transition process sets in, the DTA curve deviate from the basal horizontal line. The ferroelectric hysteresis loop was observed by applying the electric field of 6 kV/cm.