Crystallization and dielectric properties of SrO-BaO-Nb2O5-SiO2 tungsten-bronze glass-ceramics

The crystallization and dielectric properties of SrO-BaO-Nb2O5-SiO2 glass-c eramics have been investigated. Glass-ceramics that contain strontium bariu m niobate (SBN) as a primary crystalline phase, which has a tungsten bronze structure, are produced. The formation of crystalline secondary phases als o has been studied. The SBN phase shows evidence of both surface nucleation and bulk nucleation, and the crystals have an average composition of Sr0.4 7Ba0.53Nb2O6. The dendritic morphology of the SBN crystals has been examine d. The SBN content and composite dielectric constant each has been studied as a function of heating temperature/time. The highest SBN content and diel ectric constant obtained in the present study are 42 vol% and 180, respecti vely. The dielectric constant of the glass-ceramics is determined primarily by the SBN content and the residual glass phase. The dielectric constant o f the randomly oriented SBN crystal in the glass-ceramics is calculated, us ing dielectric mixture rules, to be similar to 400.