Study On Hydrothermal Synthesis Of Barium Titanate Powders

As a typical perovskite structured oxide, Barium titanate ?BaTiO₃? has high application value in martial and demotic electronic machine because of its high permittivity, low dielectric loss. With the development of microelectronic devices in miniaturization and lightweight, the quantity demanded of MLCC with high capacity and performance is steadily on the increase. It is an effective measure for accelerating the development of MLCC to realize the industrial production of superfine BaTiO₃ powders with high purity and uniform distribution.Ba?OH?₂ · 8H₂O as barium source, Ti?OC₄H₉?₄ and TiO₂ including 30% rutile and 70% anatase as titanium source respectively, BaTiO₃ powders were synthesized hydrothermally. The main results as follows:K With Ba?OH?₂·8H₂O and Ti?OC₄H₉?₄ as materials, BaTiO₃ powders were prepared hydrothermally with NH3·H₂O as mineralizer, ethanol and H₂O as solvents and NaCl solution as the additive, the effect of reaction temperature, reaction time, the mole ratio of Ba/Ti, the concentration of Ba2+, the hydrolysis of Ti?OC₄H₉?₄, the volume amount of ethanol and Cl" on the BaTiO₃ particles' characteristic had been studied. Porous BaTiO₃ paricles changed into cubic BaTiO₃ with the increase of temperature from 100? to 200 ?, whose average size is 135nm with smooth surface and symmetry; on the condition of low ratio of Ba/Ti, reaction time has a slight impact on the transformation of cubic into tetragonal BaTiO₃; the raising of the mole ratio of Ba/Ti and the concentration of Ba2+ facilitated the appearance of tetragonal BaTiO₃; the hydrolysis of Ti?OC₄H₉?₄ and ethanol didn't affect the particles'morphology deeply, but had an influence on phase, the optimum volume ratio of ethanol to Ti?OC₄H₉?₄ and Ti?OC₄H₉?₄ to water was 0.6 and 1.7 respectively. Ultrafine BaTiO₃ powders with high tetragonal content were producted without the addition of Cl-.2?BaTiO₃ powders had no obvious microscopic changes when the heating temperature increase gradually from 600 ? to 1200?, but the splitting degree of ?200? diffraction peak was enhanced during the heating process, the value of c/a exceeded 1.009 at 1200?, meanwhile the Curie temperature was 129? detected by DSC, BaTiO₃ powders were sintered into massive bulk at 1300?.3?BaTiO₃ powders were prepared hydrothermally with TiO₂ and Ba?OH?₂·8H₂O without any addition or mineralizer. During the process of investigating the effect of process conditions on morphology formation of BaTiO₃, hollow bowl-structure BaTiO₃ was formed.Different morphology of BaTiO₃ appeared on the condition of different reaction temperature and time; the tetragonality of hollow particle was lower than the solid particles' value. Based on the morphology evolution with reaction time and the result obtained by DSC that the content of Ba was larger than that of Ti, the formation machenism of hollow bowl structure BaTiO₃ was proposed.