Crystalline phases and second harmonic intensities in potassium niobium silicate crystallized glasses

Crystalline phases and second harmonic (SH) intensities in crystallized glasses of K2O–Nb2O5–SiO2 are examined, and the correlation between them is clarified. Crystallization behaviors depend strongly on SiO2 contents, and three stable crystalline phases of KNbSi2O7, K3Nb3Si2O13 and KNbO3 phases are formed in fully crystallized glasses. The crystallized glasses consisting of only perovskite-type KNbO3 phase are fabricated in the glasses with high K2O contents such as 40K2O · 20Nb2O5 · 40SiO2. The crystallized glasses containing KNbSi2O7 or KNbO3 phase show large SH intensities. The formation of K3Nb3Si2O13 phase is confirmed, and it is also demonstrated that this phase exhibits a second-order optical nonlinearity. Prior to the formation of three stable crystalline phases, it is found that various kinds of metastable crystalline phases showing second harmonic generations are formed. A transparent crystallized glass consisting of a metastable phase is fabricated.