The structure of model glasses of the amorphous phase of glass-ceramic glazes from the SiO2Al2O3CaO MgO Na2O K2O ZnO system

Abstract In this work, particular attention was paid to the structural characteristics of the amorphous phase in glass-ceramic glazes from the SiO2 Al2O3 CaO MgO Na2O K2O ZnO system. The study was carried out on model glasses whose chemical composition corresponds to the chemical composition of the vitreous phase of the glazes determined on the basis of electron probe micro-analyzer (EMPA). Structural investigations of the obtained model glasses were carried out using the mid-infrared (MIR) and solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The solid-state MAS-NMR study carried out on 27Al and 29Si nuclei showed that all aluminum and silicon ions have tetrahedral coordination and thus form the glass network. The results of the 29Si solid-state MAS-NMR measurements also showed that with the increase of ZnO content in the glass chemical composition, the number of Q3 and Q2 silicon-oxygen units increases at the expense of Q4 (where n is the number of bridging oxygens), thus indicating an increase in the degree of depolymerization of the alumino-silico-oxygen network of studied of glasses. Analysis of the MIR spectra of the obtained glasses confirmed the conclusions from the solid-state MAS-NMR research, i.e. that Zn2+ ions cause depolymerization of the glass network of glazes. The weakening of the network of glasses resulted in lowering of the transformation and dilatometric softenings temperature. The tests carried out on model glasses allow drawing conclusions about the structure and properties of the vitreous phase of real glazes.