Preparation And Dielectric Behaviors Of Barium Strontium Titanate Solid Solutions Prepared By Chemical Route

Barium strontium titanate(BST) materials have characteristics such as high dielectric constant,small dielectric loss and low Curie temperature.The paraelectric barium strontium titanate has the potential applications in the fields of cell capacitor of the dynamic random access memory devices(DRAMs),tunable microwave device applications.Recently,Investigation of BST has been continued growth.Sol-gel method can solve the problem of inhomogeneous composition existed in the solid reaction method.But the raw materials used in sol-gel method usually are high cost.In this paper, Ba_0.6Sr_0.4TiO₃ powders were prepared by a practical sol-gel process using the low cost carbonates as the substitute of acetates.The results showed that the cubic Ba_0.6Sr_0.4TiO₃ powders could be synthesized at 700℃for 0.5 hour,and the nano-particle sizes were 110nm,80nm and 20nm measured by the centrifugal method,SEM and XRD respectively.The sintering temperature of BST prepared by conventional solid state reaction route is about 1400℃.In this paper,the relative density of Ba_0.6Sr_0.4TiO₃ ceramics sintered at 1300℃and 1330℃for 2 hours reached 93.4%and 97.1%,andthe grain sizes were about 1μm.With the decreasing of grain size,Curie temperature decreases and the dielectric peaks of Ba_0.6Sr_0.4TiO₃ ceramics become lower and broader.The dielectric loss of Ba_0.6Sr_0.4TiO₃ ceramics sintered at 1330℃was about 0.002 at room temperature while had a good temperature stability.Rare earth especially lanthanide elements played an important role in function ceramics modification as additives.Ce₂O₃-doped Ba_0.6Sr_0.4TiO₃ ceramics were sintered at 1330℃for 2 hours.With the increasing of the Ce³⁺ content,curie temperature decreases and the dielectric peaks of Ce₂O₃-doped Ba_0.6Sr_0.4TiO₃ ceramics become lower and broader.The dielectric loss had obvious improvement after the doping of Ce³⁺.The value of the dielectric loss decreased at first then increased,and the dielectric properties showed the best performance when the Ce³⁺ content was 1.0mol%.This study provided a practical method for preparing BST ceramics with high quality,which possesses the features of low cost and environmental-friendly technology.This BST ceramic with fine and uniform microstructue,low dielectric loss and good temperature stability has a good potential of application.