Effect of glass composition on the interactions between structural elements in Cu-containing silicate-phosphate glasses

The structure of silicate-phosphate glasses from the SiO-P O-KO-CaO-MgO-CuO system acting as slow release fertilizers, containing different amounts of copper ions replacing magnesium or calcium ions, was examined by DSC, XRD, P, and Si MAS-NMR techniques. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The studies showed that regardless of the kind of replaced components, the Cu ions prefer to associate with the phosphorous Q units, forming the domains composed of orthophosphate with P-O-Cu bonds. The formation of domains with chemically stable P-O-Cu bonds resulted in poorer glass solubility under conditions simulating the natural soil environment. © 2014 The Author(s).