An investigation of LnUO4 (Ln = Dy and Ho): structures, microstructures, uranium valences and magnetic properties

Abstract The phase formation, structures, microstructures, uranium valences and magnetic properties of LnUO4 (Ln = Dy and Ho) were investigated. Although sintering of the precursors in argon at 1450 °C for seven days and 1400 °C for six hours both resulted in the desired phase, sintering at higher temperature for longer duration led to the formations of well crystalized lanthanide monouranates with much better homogeneity. Cubic fluorite structures were determined using X-ray diffraction data, which was confirmed with transmission electron microscopy and Raman spectroscopy. The nature of pentavalent uranium was verified with a combination of diffuse reflectance and X-ray photoelectron spectroscopies. The magnetic suseptability measurements revealed that they are paramagnetic with no long-range magnetic orders, likely due to the extensive short-range oxygen defects. Overall the improved structural and spectroscopic understandings of LnUO4 have implications in nuclear materials especially for potential accident tolerance fuels and spent fuel management.