Thermal Products in the System of NaPO3 Glass-Al2O3

The glassy and crystalline products were made by heating a mixture of aluminum oxide and sodium metaphosphate glass with P/Al ratios in the range from 1.0 to 300 at 1000 °C for 3 hr. The crystalline substance was present in the products with P/Al ratios smaller than 5.0 and was, except for aluminum oxide, always aluminum orthophosphate. The quantitative analysis and the measurement of the average chain length of the phosphates contained in the soluble parts of the products showed that aluminum oxide reacts with sodium metaphosphate to make Al–O–P linkages. A theoretical treatment of the average chain length of the polyphosphates present in the aluminate-phosphates was also made. By comparing the calculated average chain length with the measured one, it has been concluded that the most reasonable chemical structure of the glassy products of the aluminate-phosphates is Al(OP)3. By the analysis of the infrared spectra of the thermal products, four-way branching points may be said to exist in the glassy products.