Synthesis, optical and thermal characterization of NaPO$_{3}$ glass.

We have synthesized the stoichiometric bulk glass by reacting equimolar amounts of Na$_{2}$CO$_{3}$ and P$_{2}$O$_{5}$, and handling the anhydrous starting materials and reacted product in a dry ambient environment. The bulk glass displays a T$_{g}$ of 306(2)\textdegree C and an enthalpy of relaxation of 0.26 cal/gm using MDSC. In a previous report a T$_{g}=$ 287\textdegree C was obtained$^{1}$ using DSC. The glass was crystallized and characterized by XRD and revealed a powder pattern that is in excellent agreement with the known structure (CSD 174021). Raman scattering of the glass revealed prominent modes of symmetric vibration of the PO$_{4}$ tetrahedra bearing P-O$_{br\, }$and$_{\, }$-P-O$_{ter}$ bonds near 684 cm$^{-1}$ and 1162 cm$^{-1}$ respectively. The integrated intensity ratio R of the 1162 cm$^{-1}$/684 cm$^{-1}$ modes is close to 1.0(1) in the crystal but increases to 1.4(1) in the glass reflecting the finite length of the P-O-P chains in the latter. The highest frequency mode is a weak feature near 1268 cm$^{-1}$, which coincides with the TO response in IR reflectivity of the glass, suggesting that it represents the TO mode of the NaPO$_{3}$ glass.