Powder synthesis of barium titanate and barium orthotitanate via an ethylene glycol complex polymerization route

Pure and reactive barium titanate (BaTiO₃) and barium orthotitanate (Ba₂TiO₄) powders have been synthesized by an ethylene glycol (EG), polymerization-complexation route. The EG content affected the crystallization behavior and powder morphology. The BaTiO₃ powder, which had a particle size of approximately 100 nm, crystallized from amorphous to tetragonal phase on calcining at 700 °C for 1 h. Ball-milled BaTiO₃ powder sintered to 97% relative density at 1200 °C after 2 h, with a grain size of approximately 200 nm. Ba₂TiO₄ powder required longer holding times or higher temperatures to be crystallized from the amorphous phase than did BaTiO₃. In Ba₂TiO₄, the phase transformation between low-temperature monoclinic symmetry to high-temperature orthorhombic symmetry was observed by dilatometry and differential scanning calorimetry. A volume decrease of approximately 0.5% accompanied the monoclinic-to-orthorhombic transformation on heating. The high-temperature orthorhombic phase could be retained down to room temperature by the addition of at least 6 wt% magnesia (MgO) stabilizer.