KNbO3-Nb2O5 glasses were prepared with molar ratio of K/(K + Nb) from 0.16 to 0.5 by using a twin-roller quenching apparatus. Most KNbO3-Nb2O5 glasses crystallized to stable phases such as KNbO3, K2Nb4O11, K3Nb7O19, KNb3O8 and K2Nb8O21 via metastable phases after heat treatment and K4Nb6O17 glass directly crystallized to K4Nb6O17 crystal. KNbO3 glass consisted of the corner-shared NbO6 octahedra, while the amounts of the edge-shared NbO6 octahedra in the KNbO3-Nb2O5 glass structure increased with decreasing K+ ion content. The band gap energies and the ionic conductivity of the KNbO3-Nb2O5 glasses increased with increasing K+ ion content, but the density and the activation energy of the ionic conduction decreased. The glasses possessed high dielectric constants appfoaching those of ferroelectric crystals at high temperature around the crystallization temperature. The dielectric constants of the glasses, however decreased greatly with decreasing temperature and with increasing frequency.
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