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

Abstract

(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.