BST CERAMICS OBTAINED BY HYDROTHERMALLY ASSISTED COMPLEX POLYMERIZATION METHOD

Abstract

Barium strontium titanate powder Ba0.8Sr0.2TiO3 (BST) has been obtained by hydrothermal treatment of precursor solution containing titanium citrate, previously prepared by complex polymerization method, and barium and strontium acetates. The powders were calcined at 700 °C, pressed into pellets and further sintered at 1280 °C for a various sintering times (from 1 to 32 h), and structural parameters, phase composition, dielectric and ferroelectric properties were investigated. Rietveld refinement analysis of BST ceramics showed that predominant phase was tetragonal BST with monoclinic Ba6Ti17O40 (B6T17) as a secondary phase. Phase contents determined by Rietveld refinement match well with the results of energy dispersive X-ray analysis and ICP analysis. SEM micrographs of sintered samples revealed the abnormal grain growth where elongated twinned grains of BST grow in a matrix of smaller B6T17 grains. Dielectric and ferroelectric properties of BST ceramics have been correlated with density of sintered compacts, phase composition, structural parameters and microstructure. The sample sintered for 16 h showed the highest density (93% ρt), as well as the highest value of dielectric constant (~2300) and remanent polarization – Pr (2 μC/cm2) among investigated samples.