Preparation and dielectric properties of thermo-vaporous BaTiO3 ceramics

Abstract

A crystalline BaTiO3 powder was synthesized at 350°C for 0-20 h from TiO2 (> 99 % purity) and BaO (> 98 % purity) with water vapour acting as the reaction media. According to the XRD and SEM results, the BaTiO3 synthesized for 3 h proved to be the most adequate raw material for ferroelectric ceramics among the obtained samples as long as it consisted of pure crystalline sphere-shaped BaTiO3 particles with the average size of 156 nm. Pellets were pressed at (100, 150 and 200) MPa and sintered at 1300°C for 1 h. The influence of the compacting pressure on the dielectric characteristics of BaTiO3 ceramics was studied by monitoring the permittivity and loss-tangent values of the pellets at 20 Hz-2 MHz. Keywords: barium titanate, thermo-vaporous synthesis, microstructure, dielectric ceramics Kristalni prah BaTiO3 je bil sintetiziran pri 350°C od 0 do 20 h iz TiO2 (~istost: > 99 %) in BaO (~istost: > 98 %) z vodno paro kot reakcijski medij. Iz rentgenogramov in SEM-posnetkov izhaja, da je BaTiO3, sintetiziran 3 h, najprimernej{a surovina med vsemi vzorci za feroelektri~no keramiko, dokler sestoji iz~istih kristalnih okroglih delcev BaTiO3 s povpre~no velikostjo 156 nm. Peleti so bili stiskani pri (100, 150 in 200) MPa in sintrani 1 h pri temperaturi 1300°C. Vpliv tlaka pri stiskanju na dielektri~ne lastnosti keramike BaTiO3 je bil preiskovana s spremljanjem permitivnosti in velikosti izgube tg d peletov pri 20 Hz-2 MHz. Klju~ne besede: barijev titanat, termo-parno porozna sinteza, mikrostruktura, dielektri~na keramika

Structure and properties of nanocrystalline tetragonal BaTiO3 prepared by combustion solid state synthesis

“…This behavior is common for many dielectric materials [40,41]. Having in mind that the permittivity is a parameter connected with the polarization and that with higher applied frequencies less types of the polarization can be accomplished, reduction in ε r with f is clear [23,42].…”

Bi2O3-Modified Ceramics Based on BaTiO3 Powder Synthesized in Water Vapor

“…Currently, the relative density of pure BaTiO3 ceramics prepared at 1250 °C has reached only 76.3%. However, previously sintered at 1300 °C, it resulted in a density of 86.0% of theoretical [12]. The highest density among the studied samples reached 86.2% of its theoretical value and was obtained by ceramics sintered at 1225 °C with addition of 0.1 mol % Bi2O3.…”

“…This work provided novel results on the structural and dielectric properties of Bi-doped BaTiO 3 ceramics sintered from Ba-deficient powder synthesized in mild conditions of water vapor medium. Previously, non-stoichiometry of the powder was assumed to promote the growth of plate-like abnormal grains in ceramics [44] which led to a non-uniform microstructure and deteriorated the dielectric properties [12]. Currently, Ba 2+ deficit in the synthesized BaTiO 3 powder caused secondary polytitanate phase formation during the sintering and increased conductivity which manifested itself in a pronounced frequency dependence of the room-temperature dielectric constant and loss tangent of the ceramics.…”

“…A method of BaTiO 3 synthesis in water vapor atmosphere was proposed in recent works [11][12][13][14][15]. In contrast to the traditional hydrothermal method which is usually based on a reaction between the species in a solution, this method of synthesis includes the treatment of an initially dry barium and titanium oxides mixture in water vapor in equilibrium with liquid.…”

“…The corresponding ceramics possessed a homogenous microstructure, submicron grain size, and a dielectric constant of 1500-2300 at room temperature at 1 MHz. However, when sintered by the more available and widespread conventional route, ceramics based on BaTiO 3 synthesized in vapor conditions achieved lower density and had insufficient dielectric properties [12].…”