The Chemical Structures of Glasses of the NaPO3-Sb2O3-Na2O System

Abstract

Abstract Glassy and crystalline substances of the NaPO3-Sb2O3-Na2O system with P/Sb ratios in the range from 1.0 to 300 were prepared by heating NaPO3Sb2O3, and Na2CO3 at 1000°C and by then quenching the melts of the mixtures. Samples with P/Sb ratios smaller than 5.0 were obtained as crystalline substances containing amorphous substances. The chemical compositions of these crystalline substances were estimated from the data obtained by X-ray diffractometry and paper chromatography. Samples with P/Sb ratios larger than 7.0 were obtained as glassy substances. Condensed phosphates were separated by paper-chromatographic analysis, and the average degree of the polymerization of the phosphates was measured by the pH-titration method. It has been found that the crystalline substances in the samples with P/Sb ratios in the range from 1.0 to 5.0 were Sb2O5, NaSbO3, and an unknown crystalline substance. Assuming that the glasses have the P-O-P, P-O−, P-O-Sb, and Sb-O− linkages, a theoretical treatment of the degree of polymerization of condensed phosphates has been made and compared with the experimental data. It has been concluded that the glasses with P/Sb ratios larger than 7.0 have P-O-P, P-O−, and P-O-Sb linkages.