Structural characterization of ZnSO4-K2SO4-NaCl glasses

Glasses with compositions xNaCl-(50-x/2)K₂SO₄-(50-x/2)ZnSO₄, x = 0 to 30 (in mol%), were characterized via vibrational spectroscopy and X-ray pair distribution function (xPDF) analysis. The xPDF's were modeled using Empirical Potential Structure Refinement (EPSR). From the modeled xPDF, the deconvoluted xPDFs were obtained along with cation-anion coordination numbers. The sulfate environment was elucidated through analysis of the vibrational spectroscopy paired with xPDFs. As determined via these techniques, the SO₄^2- oxyanions remain as distinct tetrahedra and dominate the overall structure of these ionic glasses, even with up to 30 mol% addition of NaCl. Addition of NaCl lowers the glass transition temperature (T_g) of these materials and increases the temperature between T_g and the first crystallization temperature upon heating, as determined by differential thermal analysis (DTA). The composition-dependent xPDFs indicate that chloride ions are distributed equally and increasingly around Zn, K, and Na cations as x increases.