Necessary Conditions for the Formation of {111} Twins in Barium Titanate

Abstract

The experimental conditions for {111} twin formation in BaTiO3 were investigated. When BaTiO3 compacts without excess TiO2 were sintered either in an oxidizing atmosphere (air) or in a reducing atmosphere (95N2–5H2), no {111} twins formed within the BaTiO3 grains and no abnormal grain growth occurred. In contrast, many {111} twins were present within the abnormally grown grains in the excess‐TiO2‐containing BaTiO3 samples sintered in air, while no twins were observed in the excess‐TiO2‐containing samples sintered in 95N2–5H2. X‐ray diffraction analysis showed that excess TiO2 forms a Ba6Ti17O40 phase during sintering with the space group A2/a in air and a Ba6Ti17O40−x phase with the space group C in 95N2–5H2. It appears therefore that excess TiO2 and an oxidizing atmosphere are necessary for {111} twin formation in BaTiO3. These results may also indicate that the interface structure between BaTiO3 and Ba6Ti17O40 influences the twin formation.

Average and Local Structure of (1−x)BaTiO3−xLaYO3(0≤x≤0.50) Ceramics

“…Nowadays, there is sufficient experimental evidence that the existence of {111} twins alone does not trigger exaggerated grain growth, as initially proposed by Eibl et al 37 This is also true for LBTY ceramics, where exaggerated grain growth was not observed despite the existence of {111} twins. According to Lee et al , 38 the presence of {111} twins enhances exaggerated grain growth only when the grain boundaries are faceted.…”

Effects of TiO2 and SiO2 additions on phase formation, microstructures and PTCR characteristics of Sb-doped barium strontium titanate ceramics

“…30 In our Sb-BST and Sb-BST + TiO 2 samples, which each contained (Ba,Sr)Ti 6 O 17 and exhibited exaggerated grain growth, we did not observe any of the characteristic, elongated grains reported to be {1 1 1} twins in BaTiO 3 , and also reported in BST prepared by other research groups. 30,[41][42][43] The reasons for this discrepancy are unclear.…”

Microstructure analysis of the Y5V multilayer ceramic capacitors based on BaTiO3

“…5a), unlike BaTiO 3 sintered at low temperatures (≈1,250°C [20,21]), were observed only occasionally. Both parts (i.e., A and B) of the twin-grain appear in different contrast due to a slight deviation from the Bragg position registered by the gvectors [25], i.e., Δg ¼ g A À g B , due to obliquity.…”

“…However, no ferroelectric domains were detected from the BaTiO 3 grains. Twinning along {111} is occasionally found [20][21][22]37], both single [20,21,37] and double twins [20,21,37], as indicated by unfilled arrows in Fig. 5a.…”