The Preparing Of Porous Barium Titanate Ceramics By Freeze-casting Technology

The BaTiO3ceramics are used to produce electron device because of its welldielectric and piezoelectric property. The BaTiO3-based ceramics are used tofabricate piezoelectric ceramic, dampness transducer and aero transducer.Sensitivity is an important parameter for transducer material. The introduction oforiented pore will improve the hydro-static figure of merit of transducer materialthat used for supersonic wave checkout and the contact area between transducermatrix and medium to enhance the sensitivity of transducer.The porous BaTiO3ceramics with different suspending agent were preparedby freeze-casting technique. The fluid property of suspension and themicrostructure, dielectric properties of ceramics have been characterized by Zetapotentiometer, viscometer, scanning electron microscope(SEM) and dielectricmeasurements as a function of chemical composition and temperature. Theeffects of suspending agent variety and content on slurry fluid property andrespective stability mechanism have been researched. The effect of thepreparation process on porous BaTiO3ceramics properties was researched also.We aim to gain the porous BaTiO3ceramics with high porosity and dielectricconstant, research the effect of pore structure on porous ceramics dielectricproperties.The Kaolinite was used as suspending agent. The research result shows thatthe Zeta point and supernatant volume of BaTiO3slurry decreased and theviscosity increased as the Kaolinite content increased. When the Kaolinitecontent was8wt%, the Zeta point of BaTiO3slurry was above30mV, theviscosity was above140mPa, the supernatant volume was lower than20%. TheStable suspension was obtained with8.0wt.%content of Kaolinite. The contentof Kaolinite will affect the properties of porous BaTiO3ceramics. The porosityof porous BaTiO3ceramics first increased and then decreased as Kaolinitecontent increased. The porosity obtained maximal value74%when Kaolinite content was8wt.%. The SEM shows the samples possessed uniform distributedpore structure that oriented arrangement.The introduction of acacia gum improved suspension stability of slurry, thesuspension properties first improved and then decreased as acacia gum contentincreased. The optimal slurry was obtained by adding0.6wt%acacia gum, theaddition of Kaolinite will make the supernatant volume of slurry lower than10%,and the electrostatic steric stabilization mechanism was obtained.Based on stably suspension, the effects of sintering temperature, solidcontent, variety of suspending agent and pore structure on properties of samplewas researched. With the increase of sintering temperature, the shrinkage anddielectric constant of porous BaTiO3ceramics increased, the porosity decreasedsimultaneous. The shrinkage and porosity of porous BT ceramics decreased, thedielectric constant increased as solid content increased. The ice crystal contentdecreased as the solid content increased, so porosity decreased also. The porousBaTiO3ceramics with Kaolinite possessed columnar microstructure, and there isno curie point during temperature increasing. The porous BaTiO3ceramics withKaolinite and acacia gum possessed lamellose microstructure, and there is Curiepoint appeared during temperature increasing. The porous BaTiO3ceramicspossessed oriented pore as Kaolinite content was6.0wt.%, acacia gum contentwas0.6wt.%and solid content was10vol%.