Study On Preparation And Properties Of Ba_0.6Sr_0.4TiO₃Dielectric Ceramics

Barium strontium titanate is an important ceramic material with good optical, electronicand magnetism characters. It is widely used in the manufacturing of power capacitors, electriclight appliances, FRAM and etc. And it both has the characteristics of BaTiO3’s highdielectric constant, low dielectric loss and SrTiO3’s anti-fatigue. Also it has excellentelectrical properties. In this paper, Ba0.6Sr0.4TiO3powders by oxalate co-precipitation andmicroemulsion system method were prepared, then the powders were sintered intoBa0.6Sr0.4TiO3ceramics. It can also have high density, low porosity, high dielectric constantand low dielectric loss characteristics. Simultaneously, optimizing dielectric property of thepure Ba0.6Sr0.4TiO3ceramic through Dy2O3-doped.Ba0.6Sr0.4TiO3powders were prepared by oxalate co-precipitation method which usingbarium nitrate, strontium nitrate, titanium tetrabutoxide and Oxalic acid act as raw materialsand Dy2O3as dopant. The BST ceramics were sintered at1100℃～1280℃. Themicrostructure and dielectric property of Dy2O3-doped Ba0.6Sr0.4TiO3（the attive mol fractionwere ranged from0%to2%）were investigated by X-ray diffraction analysis(XRD), scanelectrical microscopy(SEM) and TH2818automatic component analyzer. The results indicate:The main crystal phase of sample with appropriate Dy2O3additive had a pervoskite typestructure and a certain amount of Dy3+is able to enter the lattice of BST. With the increasingof Dy2O3additive amount, the dielectric constant of materials started increasing and thendecreasing while the dielectric loss decreasing. At60kHz and20℃, with0.5wt%Dy2O3-doped Ba0.6Sr0.4TiO3ceramics have the best Combinationproperty: have the mostcompact structure and the highest dielectric constant, εr=5768.64, but the dielectric loss has alittle small: tanδ=1.18×10-4.The Ba0.6Sr0.4TiO3powders were synthesized by reverse microemulsion method. AndBa0.6Sr0.4TiO3powders were synthesized in microemulsions consisting ofwater/X-100/hexanol/cyclohexane, in which barium nitrate, strontium chloride, titaniumtetrachloride and oxalic acid were used as raw material. The microstructure and the dielectricproperties of Ba0.6Sr0.4TiO3powders were studied by X-ray diffraction analysis(XRD), scan electrical microscopy(SEM) and TH2818automatic component analyzer. The results indicatethat the crystal size of BST powders which prepared by microemulsion were smaller than thepowders which prepared by oxalate co-precipitation method. The crystal structure ofBa0.6Sr0.4TiO3powders were acicular with partical size3~5μm and diameter300~500nm. TheBa0.6Sr0.4TiO3ceramics’ dielectric constant which preparatived by this BST powders weresmall, εmin=2231.65. But dielectric loss constant have a little high.