Preparation and Sintering Behaviour of a Fine Grain BaTiO3 Powder Containing 10 mol% BaGeO3

Abstract.

J. Mater. Sci. 43 (2008) 832-838. (DOI: 10.1007/s10853-007-2195-4).

The formation of solid solutions of the type [Ba(HOC2H4OH)4][Ti1-xGex(OC2H4O)3] as Ba(Ti1-x/Gex)O3 precursors and the phase evolution during thermal decomposition of [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) are described herein. The 1,2- ethanediolato complex 1 decomposes above 589 °C to a mixture of BaTiO3 and BaGeO3. A heating rate controlled calcination procedure up to 730 °C leads to a nm-sized Ba(Ti0.9/Ge0.1)O3 powder (1a) with a specific surface area of S = 16.9 m2/g, whereas a constant heating rate calcination at 1000 °C for 2 h yields a powder (1b) of S = 3.0 m2/g. The shrinkage and sintering behaviour of the resulting Ba(Ti0.9/Ge0.1)O3 powder compacts in comparison with nm-sized BaTiO3 powder compacts (2a) has been investigated. A 2-step sintering procedure of nm-sized Ba(Ti0.9/Ge0.1)O3 compacts (1a) leads below 900 °C to ceramic bodies with a relative density of ³ 90 %. Furthermore, the cubic tetragonal phase transition temperature has been detected by dilatometry and the temperature dependence of the dielectric constant (relative permittivity) has also been measured.