Ceramics-Silikáty 48 (1) 24-28 (2004)

THE EFFECT OF B₂O₃ AND TiCl₃ ADDITION ON THE
TWIN FORMATION IN Sb₂O₃ DOPED Ti-EXCESS BaTiO₃

H. Erkalfa, B. Yuksel, T. O. Ozkan

The microstructure of B₂O₃ and TiCl₃ added Sb₂O₃ donor-doped Ti-excess BaTiO₃ compositions were investigated. Platelet type Ba₂Ti₅O₁₂ was detected as a secondary phase in the Ti excess undoped composition sintered at 1250°C for 10 hours. This phase decreased considerably in the Sb₂O₃ and B₂O₃ added samples. The Sb₂O₃ donor-doping was very effective for promoting the twin formation due to the increased concentration of the Ti⁺³ ions. The 0.5 mol% B₂O₃ addition to this composition gave rise to the polygonal type grains containing twin lamellae and Ti-rich rod-like grains. At 1 mol% the B₂O₃ addition level, the polygonal grains and twin lamellae grew to the order of 100 µm size in a fine grained matrix. A sudden grain growth occurred at 2 mol% the B₂O₃ addition level, with the loss of twin lamellae in the structure. The addition of 0.2 mol% excess TiO₂ as a liquid TiCl₃ form to the 0.5 mol% B₂O₃ containing sample, reduced the size and the number of polygonal grains and had a marked effect on the twin formation due to the homogeneous distribution of the excess Ti ions in the composition.

Keywords: Barium titanate, Twin formation, Microstructure, Grain growth