Crystallization and dielectric properties of SrO-BaO-Nb2O5-GeO2 tungsten-bronze glass-ceramics

The crystallization and dielectric properties of SrO-BaO-Nb2O5-GeO2 glass-ceramics were investigated. One- and two-stage heat-treatment methods were used to convert the parent glass to glass-ceramics. Strontium barium niobate (SBN) with a tetragonal tungsten-bronze structure formed as the major crystalline phase. When the crystallizing emperature/time was increased, the secondary crystalline BaGe2O5 phase coexisted with SBN, BaGe2O5 formed as a surface layer grown from the surface into the interior of the sample. The dendritic morphology of SBN crystals was examined. The glass-ceramics crystallized by two-stage heat treatment have higher dielectric constants than those crystallized by one-stage heat treatment. The highest dielectric constant that was obtained in the present glass-ceramics was 320. The glass-ceramics showed relaxer-type dielectric behavior.