High-temperature fluxing salt of LiNbO₃ single-crystal by potassium meta-phosphate solvent

We report that potassium meta-phosphate (KPO₃) is an adequate solvent for high-temperature fluxing salt of LiNbO₃ crystal. As the KPO₃ is used as the solvent, the solubility of LiNbO₃ is as high as 3 g g^-1 at 1050 C. The dissolving is fast. Neither solute nor solvent evaporates from the melt during the dissolving procedure. A clear solution is obtained and verified valid for crystal composition analysis using chemical method of inductively coupled plasma atomic emission spectroscopy. To help for understanding the dissolving mechanism, the obtained fluxing melt product was further characterized using X-ray diffraction, nuclear magnetic resonance and Raman scattering spectroscopy. The results show that the melt is amorphous. The P ion in the melt is in the form of low condensation and the Nb ion is likely in the form of Lindqvist ion. Finally, the dissolving mechanism is discussed.