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

摘要

Pure and reactive barium titanate (BaTiO_3) and barium orthotitanate (B2TiO_4) powders have been synthesized by an ethylene glycol (EG), polymerization- complexation route. The EG content affected the crystallization behavior and powder morphology. The BaTiO_3 powder, which had a particle size of approximately l00 nm, crystallized from amorphous to tetragonal phase on calcining at 700 deg. C for l h. Ball-milled BaTiO_3 powder sintered to 97 relative density at 1200 deg. C after 2 h, with a grain size of approximately 200 nm. Ba_2TiO_4 powder required longer holding times or higher temperatures to be crystallized from the amorphous phase than did BaTiO_3. In Ba_2TiO_4, 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 ~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.