Devitrification and dielectric properties of (Na₂O,BaO)–Nb₂O₅–SiO₂ and (K₂O,SrO)–Nb₂O₅–SiO₂ glass–ceramics

(Na₂O,BaO)–Nb₂O₅–SiO₂ and (K₂O,SrO)–Nb₂O₅–SiO₂ glass ribbons with varying proportions of alkali and alkaline earth were formed using roller quenching. (Na₂O,BaO)–Nb₂O₅–SiO₂ glasses of compositions devitrified to form Ba₂NaNb₅O₁₅ (in the form of ∼80 nm crystallites in an amorphous matrix) yielded frequency-stable dielectric constants of ∼250 and losses of ∼0.05. Such low losses and frequency stabilities were also observed from (K₂O,SrO)–Nb₂O₅–SiO₂ glasses of compositions forming predominantly KSr₂Nb₅O₆ (∼30 nm crystals), yielding dielectric constants of ∼400. Both optimized compositions showed moderate decreases in dielectric constant with increasing temperature.