| The (Ba 0.6 Sr 0.4 )Ti0 3 powder coated by silica and magnesium oxides was prepared by sol-gel method, and sintered body was produced by pressing and sintering the coated BST powder with proper fluxes. One of the advantages of sol-gel method is that the dielectric constant of silica and magnesium oxide was low, which can wash largely down dielectric constant of BST. The other is that silica and magnesium oxide coated on the surface can prevent BST particles from growing and control the particle within small size, then the dielectric properties are optimized.The BST powder was synthesized by solid reaction process, where the raw materials are barium carbonate, strontium carbonate and titanate whose mol proportion is 6:4:10. The BST is cubic and about several hundreds nanometer. Theζpotential of BST powder in water is changed from -9.61 to -31.46 after adding polyethylene glycol. It's obviously that the polyethylene glycol 1000 as disperser can improve the disperstiveness of BST powder in water.The coating layer of silica and magnesium oxides was prepared by sol-gel method. The tetraethyl orthosilicate hydrolyzes at the condition pH=2.5, then polycondensates at pH=5～8. We optimized the sol-gel process and achievedthe coated BST powder with homogeneous coating layer. The coating situation was observed by TEM and SEM. The phase transformation and products were measured by DSC/TG and XRD, then it's concluded that the coated BST powder is calcined at 950℃.The dense sintered body was made from the coated BST powder with fluxes by pressing and sintering at certain temperature. It's found that the dense sintered body is got by adding 1wt%ZnO,1wt%La 2 O 3和1wt%Li 2 CO 3 as fluxes. At the same time, the dielectric properties of good sintered body were measured and analyzed.
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