Phase relations in the Barium Titanate—Titanium Oxide System

Abstract

Phase relations in the BaTi03-Ti02 system were studied at temperatures above 1300°C in air. Quenching experiments were performed with high-purity reagents, and a new equilibrium phase diagram was constructed. Results include redetermination of the liquidus boundaries, the eutectic temperature, the melting or decomposition temperatures of the stable compounds in the system, the cubic-hexagonal transition in BaTiO,, and the solid solubility of TiOz in BaTi03. [

Microstructure and permittivity of sintered BaTiO3: influence of particle surface chemistry in an aqueous medium

“…3(A-2). However, the liquid-phase induced abnormal grain growth was not observed in this case, a result that is inconsistent with previous reports [18,19] that associated abnormal grain growth with Ti-excess. No further significant microstructural development occurred in the specimen after a 2-h dwell time, except an increase in the liquid phase content.…”

“…It has been proposed by Abicht and co-workers [10,20] that the amorphous TiO 2 surface phase formed on acid-conditioned BaTiO 3 promotes densification below the eutectic temperature of the pseudo-binary BaTiO 3 -Ba 6 Ti 17 O 40 system (1332 8C) [21], by facilitating the sliding of individual BaTiO 3 grains. Another possibility to enhance densification is impurities in the starting materials, which could decrease the liquid formation temperature [22]; the same starting powder was used for all experiments in the present study and only high purity chemicals (acid, base) and deionized water were employed, which should rule out impurities in explaining observed differences between the powders treated under different pH conditions.…”

“…The dissolution and subsequent adsorption/precipitation of Ba 2þ also create substantial problems for the control and reproducibility of dielectric properties in aqueous-based tape casting. There are a number of reports where the effects of bulk Ba/Ti ratio on sintering behavior and dielectric properties of BaTiO 3 have been described [11][12][13][14][15][16][17][18]. Although variations of Ba/Ti ratio within distinct surface layers on BaTiO 3 , as a result of Ba 2þ dissolution/precipitation, should therefore be of significant concern, this has been studied far less than the effect of bulk variations.…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…This morphology may be attributed to the presence of a liquid phase during sintering 390 , ascribed to the eutectic point that Ba 6 Ti 17 O 40 forms with BT at ~ 1320 °C. [387][388][389] Liquid phase sintering could explain the presence of intragranular porosity in coarse grains, as it was reported that intragranular porosity requires fast mobility of grain boundaries above the pore shrinkage rate. 391 A detailed sintering study would be required to corroborate the aforementioned hypothesis, which is out of the scope of this work.…”

Structural and Dielectric Studies of Fe-Li Substituted Hexagonal Barium Titanate

“…A series of hexagonal Ba (Ti,Fe) O 3 materials where Ti IV was progressively replaced by Fe III and/or Fe IV with oxygen vacancies being formed exclusively in O(1) sites within the H-BaO3 layers, has been reported [10]. It was first reported in 1960 [11] that certain amounts of Mn are sufficient to stabilize the hexagonal phase of BaTiO 3 at room temperature whereas the hexagonal polymorph of undoped material is stable in air only at temperatures higher than 1703 K [12].…”