Preparation of nano-sized ABi_2Nb_2O_9 (A = Ca~(2+), Sr~(2+), Ba~(2+)) ferroelectric ceramics by soluble Nb(V) tartarate precursor and their dielectric characteristics after sintering

摘要

AB_(12)Nb_2O_9 (A = Ca~(2+), Sr~(2+), Ba~(2+)) were prepared by using an aqueous solution method from the mixture of water-soluble M-EDTA (M = Ca~(2+), Sr~(2+), Ba~(2+)), Bi-EDTA, Nb-tartarate and TEA as the starting materials. A black fluffy mass resulted on heating the solution mixture at ～200 ℃. X-ray powder diffraction (XRD) showed that a single phase with the layered perovskite structure was formed after calcining the black fluffy mass at 600 ℃. No intermediate phase was found during heat treatment at and above 600 ℃. The particle size obtained from TEM lay between 20 and 30 nm. Structural electron microscopy (SEM) revealed that the average grain size after sintering at 900 ℃ for 4 h ranges from 1.2 to 1.67 μm with a relative compact density of ≥90%. A comparative study on dielectric constant and corresponding tangent loss were carried out at 1 kHz, 100 kHz, 1 MHz, and 5 MHz from which the Curie temperature (T_c) was found to be at 935, 450, and 170 ℃ with peak dielectric constants at 930, 595, and 545, respectively, for CBN (CaBi_2Nb_2O_9), SBN (SrBi_2Nb_2O_9), and BBN (BaBi_2Nb_2O_9) measured at frequency 100 kHz with very low tangent loss.