Preparation and structure of low-melting-point stannous chlorophosphate containing nitrogen glasses

P-Sn-O-Cl-N glasses were prepared at 275–450 °C, and the optimum melting temperature of the colorless transparent P-Sn-O-Cl-N glasses was 350 °C. Series of P-Sn-O-Cl-N glasses were further prepared at 350 °C, exhibiting an ultra-low glass transition temperature (Tg) of <140 °C; the glass-forming range were determined. The infrared (IR) and Raman spectra revealed that the Q1 and Q2 units of the [PO4] tetrahedral increased and decreased, respectively, with decreasing P/Sn ratio. The unstable P = O bond was destroyed by tin to form a longer P-O-Sn structural chain, which strengthened the crosslinking degree of the glass network structure and increased the Tg and decreased thermal expansion coefficient of the glasses. X-ray photoelectron spectrometry indicated that most Cl ions were bound to cationic Sn2+ and some to NH4+. Moreover, the low-temperature melting reduced the volatilization of Cl− and NH4+ ions, which contributed to the low-melting-point and Tg of the glasses.