Structural characteristics of MgOP 2O 5 glasses

Abstract

Previous investigators have believed that the “Phosphate Anomaly” in MgOP 2O 5 (MP) glass is due to an abrupt change in a coordination equilibrium between Mg and O ions, in which the oxygen coordination number (CN) of Mg 2+ is 6 ⇄ 4. However, we found recently that the CN of Mg is approximately 6 in MP glass with varying M/P ratio, by means of high-resolution X-ray emission spectroscopy. Thus, the density-anomaly in MP glass around M/P = 1 should not be interpreted by the change of the CN of Mg. Some speculative considerations on the structure and properties of MP glass are presented based on the results of our findings. Many facts reported by the researchers can be explained by assuming a voluminously mixing structure, in which phosphate anions in the glass of M/P = 1 mainly consist of long chain-type ions and partly of ring ions such as tetrametaphosphate. We have concluded that MP glass may have a different structure in comparison with other anomalous phosphate glasses, i.e. BeO- and ZnOP 2O 5 systems.