Crystallization and second harmonic generation in thermally poled niobium borophosphate glasses
Résumé
Crystallization of glasses with compositions (1−x)(0.95 NaPO3+0.05 Na2B4O7)+xNb2O5, x=0.4, 0.43, 0.45, 0.48 was investigated by differential scanning calorimetry and X-ray powder diffraction. Crystallization of two phases was observed in the glasses with x=0.43–0.48. First phase is a sodium niobate with the structure of tetragonal tungsten bronze (Tc~720-760°C) and second phase is Na4Nb8P4O32 (Tc~830-850°C). The crystallization of sodium niobate is correlated with increasing of nonlinear optical efficiency reported for thermally poled glasses with x>0.4...