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DF: Dielektrische Festkörper

DF 3: Poster Session

DF 3.12: Poster

Montag, 27. März 2006, 09:30–17:00, P1

Phase and microstructure evolution during BaTiO₃ formation by solid state reactions on rutile single crystals — •Andriy Lotnyk, Stephan Senz, and Dietrich Hesse — Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany

During the synthesis of BaTiO₃ ceramics out of a stoichiometric BaCO₃-TiO₂ mixture the evolution of different intermediate phases can generally be observed. These intermediate products are Ba₂TiO₄ and Ti-rich phases. Using micro chemically designed core shell powders the sequence of forming phases changes. To understand this behavior model experiments are performed using rutile (TiO₂) single crystals. The solid state reactions of TiO₂ with BaCO₃ (solid and vapour, respectively) are studied. A BaCO₃ target was electron beam evaporated in a high vacuum system with P_O2=1×10⁻² Pa. The substrates were heated in a tube furnace at T=300-500^∘C during deposition, followed by a solid-solid reaction at 575-1100^∘C in vacuum or in air; for the gas-solid reaction, the substrates were heated at T=575-1100^∘C directly during deposition. The reaction products were investigated by XRD and TEM. The solid-solid reaction at 600^∘C for 30 min under vacuum produced the metastable intermediate Ba₂TiO₄ phase while the reaction in air resulted in the formation of BaTiO₃. Well-oriented products are formed on (110), (100), (101) TiO₂ and polycrystalline phases were identified on (001) TiO₂.