Structural studies of copper-containing multicomponent glasses from the SiO2–P2O5–K2O–CaO–MgO system

Multicomponent glasses from the SiO2–P2O5–K2O–MgO–CaO–CuO system acting as slow release fertilizers were synthesized by the melt-quenching technique. The influence of CuO and P2O5 addition on the structure of glasses was evaluated by FTIR, Raman, 31P, and 29Si MAS NMR spectroscopies. The studies showed that the Cu2+ ions displacing Ca2+ ions and Mg2+ ions in the structure of glass prefer to associate with the phosphorus Q1 species, forming the Q0 species with chemically stable POCu bonds. This is accompanied by the reduction of the degree of polymerization of the phospho-oxygen sub-network, with a simultaneous increased degree of polymerization of the silico-oxygen sub-network of the silicate–phosphate glasses.