On the formation of an oxycarbonate intermediate phase in the synthesis of BaTiO3 from (Ba, Ti)-polymeric organic precursors

• Published in: Journal of the European Ceramic Society 2002-06, Vol.22 (6), p.797-807
• Main Authors: DURAN, Pedro, GUTIERREZ, Dionisio, TARTAJ, Jesus, BANARES, Miguel A, MOURE, Carlos
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Inorganic chemistry and origins of life; Niobates, titanates, tantalates, pzt ceramics, etc; Physics; Preparations and properties; Salts
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/s0955-2219(01)00392-2

Although not well crystallised, thermoanalytical measurements, the unique XRD pattern, and new IR, Raman, and 13C NMR structural features revealed that a metastable intermediate oxycarbonate phase has a stoichiometry close to Ba2Ti2O5CO3, which is characterised by having CO3(2-) groups different from those of pure BaCO3 located, probably, in an open interlayer BaTiO3 metastable structure. From the XRD crystal size measurements and Raman spectra, it was suggested that the thermal decomposition of the (Ba,Ti) citrate polymeric organic precursor above 550 C led to the formation of a mixture of tetragonal and hexagonal BaTiO3 polymorphs rather than cubic. Despite the specific surface of the synthesised BaTiO3 powders up to 700 C, higher than 40 m2/g and an equivalent particle size smaller than 25 nm, Raman spectra indicated asymmetry inside the TiO6 octahedra of the BaTiO3 structure. 31 refs.