Site Occupancy and Dielectric Characteristics of Strontium Barium Niobate Ceramics: Sr/Ba Ratio Dependence

The tetragonal tungsten bronze type of SrxBa1-xNb2O6 (SBN, 0.3≤x≤0.7) ceramics was synthesized using the solid state reaction method and the dielectric properties of SBN ceramics as a function of the Sr/Ba ratio were examined. With an increasing Sr/Ba ratio in SBN ceramics, the Curie temperature decreases while the maximum dielectric constant at the Curie temperature increases. The relaxor behavior of the SBN ceramics as a function of the Sr/Ba ratio was quantitatively evaluated. The relaxor behavior of the dielectric constant became stronger as the ratio of Sr/Ba increased. In the composition where x=0.4, the degree of diffuse phase transition (DPT) was lowest because Sr and Ba ions exist only in the A1 and A2 sites, respectively, different from other composition. Various situations in which the Sr and Ba cations occupy the A1 and A2 sites were considered as a function of the Sr/Ba ratio. A relationship between DPT behavior and ion ordering at A1 and A2 was analyzed theoretically as a function of the Sr/Ba ratio. The experimental results are explained from the viewpoint of tungsten bronze crystallography of SBN ceramics.