Crystallization and nonlinear optical properties of potassium niobium silicate glasses

The crystn. of the xK2O.xNb2O5.(1-2x)SiO2 (x = 0.167 - 0.250) glasses and glasses close in compn. to K2O.Nb2O5.4SiO2 at the K2O:Nb2O5 ratio ≠ 1 is investigated. In high-silica glasses, the metastable phase sepn. followed by the bulk multiphase crystn. are obsd. at temps. close to the glass transition point, Tg. The nanostructured transparent glasses that exhibit the optical second harmonic generation (SHG) effect are formed at the early stages of phase sepn. The surface crystn. of glasses with the pptn. of the KNbSi2O7 noncentrosym. phase occurs at higher temps