Ceramics-Silikáty 37, (4) 177 - 180 (1993)

BaTi₃O₇ is formed in the BaTiO₃⁺TiO₂ mixtures by the solid state reaction as well as in molten salts medium in the temperature and time intervals of 800 - 1200 °C and 1 - 4 h, respectively. In the presence of liquid phase BaTi₃O₇ formation rate is higher then that in the solid state. While in the solid state reaction the maximum conversion degree was ca 50 %, in the presence of the flux the conversion degree attains ca 70 % at the temperature of 1470 K. The conversion degree is favourably influenced also by the increasing temperature of the isothermal heating. The reaction time is not influenced by the reaction time in the range from 1 to 4 h, however, it affects the average size of the BaTi₃O₇ crystals. The activation energy of the BaTi₃O₇ formation has the value ΔE = 130 kJ/mol for the reaction in the liquid as well as in the solid state. The isothermal heating of the stoichiometric mixtures BaSO₄+Na₂CO₃+TiO₂ and BaCl₂+Na₂CO₃+TiO₂ at the temperatures of 700-900 °C to produce BaTi₃O₇ was not successful. The obtained product contained the mixture of BaTiO₃ and Na₂TiO₃.