Synthesis and structural characterization of dry AgPO₃ glass by Raman scattering, infrared reflectance, and modulated differential scanning calorimetry

The glass transition temperatures of AgPO₃ have been reported to lie in the 163<T_g<192 °C range. These results are typical when precursors are processed at laboratory ambient. In the present work, we show that if precursors are handled in a dry ambient environment, the T_g’s steadily increase in the 181(2)<T_g<254(2) °C range as the relative humidity of the ambient environment decreases. The glass transition temperature of dry AgPO₃ is found to be 254(2) °C. We have compared the vibrational densities of states of the low-T_g [181(2) °C] and high-T_g [254(2) °C] samples in Raman scattering and ir reflectance measurements. The ir reflectance shows the presence of both free and bonded water in the low-T_g [181(2) °C] samples, but the concentration of both species decreases in the high-T_g [254(2) °C] samples. In Raman scattering, the boson peak scattering strength increases, and the scattering strength ratio R of the P-O_t (terminal) to the P-O_b (bridging) mode of the P-O-P- chains decreases as the sample T_g increases. The presence of bonded water serves to scission the P-O-P chain network by replacing bridging O_b oxygen sites with terminal OH⁻ species; and once incorporated, bonded water is difficult to remove.