Abstract
Abstract Undoped and MgO-doped TiO2- and BaO-excess non-stoichiometric barium titanate (BaTiO3) compositions were pressureless sintered using a conventional furnace and CO2 laser. High-temperature hexagonal BaTiO3 was metastably retained to room temperature as revealed by both X-ray diffractometry and transmission electron microscopy. The sintered microstructure of the TiO2-excess composition is characterized by a bimodal grain size distribution containing large plate-like grains. The microstructure of BaO-excess BaTiO3 with MgO doping is characterized by large spherulitic grains with petals 1–2 mm long. Hexagonal phase retention in the undoped material is only obtained when quenching the laser sintered BaO-excess powder. However, it occurs in both non-stoichiometric BaTiO3 compositions with MgO doping, regardless of the sintering techniques. A possible mechanism for the hexagonal phase stabilization associated with oxygen vacancies is discussed.
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