Preparation of nano-sized ABi₂Nb₂O₉ (A = Ca²⁺, Sr²⁺, Ba²⁺) ferroelectric ceramics by soluble Nb(V) tartarate precursor and their dielectric characteristics after sintering

ABi₂Nb₂O₉ (A = Ca²⁺, Sr²⁺, Ba²⁺) were prepared by using an aqueous solution method from the mixture of water-soluble M-EDTA (M = Ca²⁺, Sr²⁺, Ba²⁺), Bi-EDTA, Nb-tartarate and TEA as the starting materials. A black fluffy mass resulted on heating the solution mixture at ∼200 °C. 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 °C. No intermediate phase was found during heat treatment at and above 600 °C. 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 °C 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 °C with peak dielectric constants at 930, 595, and 545, respectively, for CBN (CaBi₂Nb₂O₉), SBN (SrBi₂Nb₂O₉), and BBN (BaBi₂Nb₂O₉) measured at frequency 100 kHz with very low tangent loss.