PNNL

Abstract

Glasses with compositions xNaCl-(50-x/2)K?2SO?4-(50-x/2)ZnSO?4, 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 SO?4?2- oxyanions remain as distinct tetrahedra and dominate the overall structure of these ionic glasses, even with up to 30mol% 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.