Doping Modification Of Textured Based SrBi₂Nb₂O₉Ceramics Specialized Subjects: Inorganic Chemistry

SrBi₂Nb₂O₉is a member of Aurivillius-type bismuth layer-structured perovskiteferroelectrics, in which the pseudo-perovskite layers are interleaved with bismuthoxide layers,（Bi2O2）²⁺. SrBi₂Nb₂O₉has a lead-free composition, high Curietemperature, low dielectric constant, high resistivity, and large crystalline anisotropyBased on anisotropy of the three-dimensional structure of flake grain, due tothe particles are easy to prepared by molten salt method. Highly textured SYBNceramics with enhanced electrical properties were easily fabricated by grainorientation technique. The degree of orientation increases with the addition of dopant,thus to improve the electrical properties of the ceramic. It is a promising to fabricatethe valuable ceramics product.The seed-crystal platelets were fabricated by MSS, The reactant is dissolved inmolten salt medium to diffuse, decompose and react, forming the big size platelets viathe molten salt medium, which is easy to grow up to be the anisometric particle. Thenthe slurry was degassed under vacuum and tape-casted on a plate glass surface Afterdrying, curing, cutting piece, pelleting forming, plastic and high temperature sintering,after a series of process operation, textured fine ceramics are prepared.The mixture was calcined at900oC for2h to get anisotropic particles.With the30wt%organic material content of organic carrier, which can get the best pasteviscosity of the fluid. The experiment results show that the grains in the process ofhigh temperature sintering in clusters.After the ceramics electrical performance testing, it is shown that structure of thetextured ceramics has the obvious anisotropy. To suppress oxygen vacancies in the perovskite layers to improve the electrical properties by replacing A-B site withdifferent ionics.The effect of grain orientation on dielectric loss, dielectric constant ofhot-forged SrBi₂Nb₂O₉ceramics with A-site doping is more obvious than that withB-site doping. In addition, With the perovskite layer doping ion partially enters thebismuth oxygen layer which partly compensates the volatilization of the bismuthatoms.In the analysis of the effect on kinds of doping ions and the molar concentration toceramic consistency, it was found that the doping ions which enters the bismuthoxygen layer shows a distinct relationship with their radius size. Because thechanging of ions radius broke the tolerance factor in bismuth layer-structure.The degree of orientation increases with the addition of Y³⁺dopant, which reachesto nearly87%, the dielectric loss is0.017,the dielectric constant amount to151in thedirection perpendicular to the tape-casting plan. With doping Nb5+, the degree oforientation reaches to nearly90%, the dielectric constant amount to90in the directionperpendicular to the tape-casting plan.