Effect of the excess of bismuth on the morphology and properties of the BaBi_2Ta_2O_9 ceramics

摘要

In this study the effect of bismuth content on the crystal structure, morphology and electric properties of barium-bismuth-tantalate (BBT) ceramics was explored with the aid of X-ray diffraction (XRD), scanning electron microcopy (SEM), dielectric properties and ferroelectric hysteresis loops. BaBi_2Ta_2O_9 (BBT) ceramics have been successfully prepared by the solid-state reaction. The BBT phase was crystallized at 900 deg C for 2 h. The excess of bismuth controls the grain size, affecting the density of the material. Measurements of dieletric constant and dielectric losses confirm that the material is a ferroelectric with a Curie temperature around 77 deg C. The dieletric constant measured at room temperature was 400, with a dielectric loss of 0.03. Both the phase-transition behaviour and ferroelectric properties, such as spontaneous polarization (P_s)- showed a dependence on Bi content.