Preparation Of Nano-Sized BaTiO₃ Powders

BaTiO₃ powders of particle size ranged from 14¹60nm and cubic phase structure were prepared by a two-step precipitation route, a sonochemical method and a solvothermal process, respectively, in which TiCl₄, Ba(OH)₂·8H₂O and NH₃·H₂O were used as raw materials, and ethanol,water and the mixture of them as reactive medium. The as-prepared powders were characterized.A two-step precipitation route was employed to synthesize BaTiO₃ powders and～17nm powders were obtained at 75℃. The experimental results showed that the crystallization temperature should be higher than 60℃; within the range of 60～80℃, reaction temperature affected hardly the particle size; higher reactant concentration was benifit to obtain finer powders; BaTiO₃ particles can be obtained at the reaction time of longer than 0.5h, and the prolonged time has a tend of increasing the particle size of the powders.Nano-sized spherical BaTiO₃ particles with particle size ranged from 14⁶0nm were synthesized by a sonochemical method at 75℃. It was found that particle size of the powders increased with the increase of ultrasonic irradiation intensity; compared with conventional stir, ultrasonic irradiation introduced was benifit to synthesis BaTiO₃ powders with smaller particle size, uniformy distribution and few aggregates.About 70nm BaTiO₃ particles with cubical morphology were prepared at 200℃by a solvothermal process, under the staring conditions of Ti⁴⁺ concentration of 0.1mol/L, Ba/Tl molar ratio of 1.6:1, 90% ethanol-water aqueous medium, NaOH concentration of 2mol/L. The results showed longer reaction time and higher reactants concentration were in favor of increasing the particle size.The characteristics of sintering behavior of BaTiO₃ ceramic were obtained by means of a method of thermal anlysis. It was found that sintering temperature of BaTiO₃ ceramics was confirm in 1150-1250℃. The powders obtained by three methods as mentioned above were sintered according to same sintering conditions by a. two-step pressureless sintering, and the maximal relative density reached 98.9%, dielectric constant at room temperature of 3834, the delectric loss of 0.037.