Structural analysis of the thermal conversion of metal chlorides into phosphate glasses

The conversion reaction of metal chlorides (NaCl, KCl, PbCl2, CdCl2) into phosphate glasses is studied via a structural approach. The glass compositions are: Na: 8.5–15.4%; K: 7.4–13.2% ; Pb: 1.6–2.6%; Cd: 0.4–0.7%; Cl: 0.2–20.1%; P: 11.6–20.4%; O: 36.5–60.8% (at. mol%).31P magic-angle-spinning nuclear magnetic resonance and 31P double quantum analyses are employed for determining the structural evolution of the phosphate network as function of the batch composition and the melting temperatures (700°C and 900°C). The Q1/Q2 ratios, measured by 31P spectrum deconvolution, are in accordance with the elemental analyses of the samples prepared at 700°C and 900°C. 23Na magic-angle-spinning nuclear magnetic resonance shows the presence of sodium in the amorphous phases and in NaCl crystals in devitrified samples. Transfer of populations in double-resonance experiments (TRAPDOR) are also consistent with the hypothesis that there is no specific bonding of sodium to a particular Qn unit in the phosphate network.