Structural study of Nd oxidation by means of in-situ synchrotron X-ray diffraction (400 ≤ T ≤ 700 °C)

• Oxidation of metallic Nd has been followed by synchrotron X-ray diffraction vs. T.
• Between 200 and 700 °C the hexagonal and the cubic phase coexist.
• At each considered temperature the cubic phase is fully oxygenated.
• The hexagonal form shows continuous oxygen depletion with increasing temperature.

The existence of pure cubic Nd2O3 is a debated issue in the literature, as it seems to depend on the nature of the oxide precursors and on the synthesis parameters. In this work, Nd2O3 was produced by Nd oxidation, treating first the metal powders in O2 atmosphere (P = 1.05 atm) at low temperature (200 and 350 °C) and then heating the resulting partially oxidized Nd at temperatures ranging between 400 and 700 °C; the structural modifications were followed by in-situ synchrotron X-ray diffraction. Collected data were refined by the Rietveld method and the results revealed that a mixture of hexagonal-Nd2O3 and cubic-Nd2O3, with almost constant amounts of the two components, formed in the whole temperature range; moreover, an incomplete oxygenation of the hexagonal phase occurred, while the cubic structure is fully oxygenated at each temperature considered.