Effect of molybdenum oxide addition on the durability and structure of iron phosphate glasses

Abstract

Molybdenum oxide (MoO₃)-containing iron phosphate (Fe–P) glasses with an analyzed Fe/P molar ratio of 0.41–0.43 and 0–43 mol % MoO₃ were prepared via a conventional melt-quenching method. The X-ray diffraction analysis revealed that all prepared samples had an X-ray non-crystalline state with a halo pattern. The dependency of the MoO₃ concentration on the glass transition temperature and water durability were evaluated. The water durability was examined in terms of glass plates with dimensions of 10 × 10 × 3 mm³ via a static leaching test at 120 °C for 72 h using ultrapure water. Raman spectroscopy was used for the analysis of the PO₄ Qⁿ structures (n = 0, 1, 2) and the Mo⁵⁺/Mo⁶⁺ species. The Fe–P glasses containing 8–17 mol % MoO₃ consisted mainly of PO₄ Q¹ structural units as well as both Mo⁵⁺O₆ distorted octahedra and Mo⁶⁺O₆ octahedra and a Fe-related polyhedra with a minimization of P–O–P and Mo–O–Mo bonds. These structural features were qualitatively related to the improved properties of both thermal stability against crystallization and water durability for the MoO₃-containing Fe–P glasses.