KTiOPO4 precipitation from potassium titanium phosphate glasses, producing second harmonic generation

Glass formation in the K2O-TiO2-P2O5-SiO2 system, and the structure and crystn. behavior of glasses having compns. near the stoichiometry of KTiOPO4 (KTP) have been examd. by DTA, X-ray diffraction (XRD), fast Fourier transform IR (FTIR) spectroscopy and second harmonic generation (SHG). Pure glasses may be obtained adding an appropriate amt. of P2O5 as well as SiO2 to the KTP compn. Transparent and homogeneous glasses were synthesized for the 56(K2O·2TiO2·P2O5)·44P2O5 (KTP-44P) and the 90(K2O·2TiO2·P2O5)·10SiO2 (KTP-10Si) molar compns. In contrast, for the 80(K2O·2TiO2·P2O5)·20SiO2 (KTP-20Si) and for higher SiO2 contents, the obtained glasses were partially opaque and phase sepd. KTP glasses with lower P2O5 content cannot be obtained as they crystallize during quenching. The KTP-10Si glass shows the only exothermic peak connected to KTP phase crystn. whereas the KTP-44P and the KTP-20Si glasses devitrify in two steps. Firstly the same unidentified phase is formed in both these glasses and the KTP phase is formed only at higher temps. Transparent and opalescent KTP glasses exhibiting SHG activity may be produced by careful heat treatments at temps. just above Tg. The origin of SHG in transparent glasses is presumed to be connected with either pptn. of KTiOPO4 nanocrystallites or very early stages of liq.-type phase sepn.