The properties of BaTiO3 as a material for manufacture of functional ceramics (e. g. PTCR-thermistors, capacitors) are influenced especially by the properties of BaTiO3 basic powders. The development of new methods for preparation and modification of such powders as well as detailed knowledge about established methods are necessary staring points due to control these properties. Especially the preparation and investigation of model substances are regarded as a key for solving controversially discussed phenomena dealing with powder-preparation and sintering of BaTiO3. Based on technologies of spray drying and newly developed spray hydrolysis, modern strategies for production and modification of metal oxides (BaTiO3, TiO2, Ba6Ti17O40) could be established. In such a way, it for the first time succeeded to prove that the controversially discussed phase Ba2Ti2O5CO3 is a crystalline and chemically homogeneous compound. This evidence was shown by electron microscopic (HREM) and spectroscopic (FTIR) measurements during the thermally activated genesis from amorphous to crystalline BaTiO3. The BaTiO3-formation mechanism could be investigated (PEMK, TEM, EDX, DTA, XRD) at core-shell structured TiO2-BaCO3 mixtures, for the first time. Towards the previous state of knowledge this mechanism includes the formation of titanium-rich barium titanium polytitanats (BaTi5O11, BaTi4O9, BaTi2O5) too. These intermediate phases are constituted themselves sequentially according to the TiO2/BaO-phase diagram. The pressing and sintering properties of BaTiO3 based powders could be controlled due to coating with polyvinyl alcohol, TiO2 and Ba6Ti17O40, respectively. |