EPR investigations of Fe3+ in single crystals and powders of the zircon-structure orthophosphates LuPO4, YPO4, and ScPO4

Iron-doped single crystals of the zircon-structure orthophosphates LuPO4, YPO4, and ScPO4 have been grown by means of a flux technique. Corresponding powders have been prepared independently by a urea precipitation technique and electron paramagnetic resonance measurements demonstrate that the Fe3+ impurity is situated in the same substitutional site in both the single crystals and the powders for all three hosts. The sign of the crystal field parameter b02 is shown to be positive (opposite to that found for Gd3+ in these hosts). The crystal-field splittings were found to be largest for the scandium host and smallest for the yttrium host. The EPR results show that iron can be incorporated in a substitutional crystallographic site in material prepared by either a high temperature process or by a low temperature precipitation and calcination (∼800 °C), and these findings have implications for the use of lanthanide and related orthophosphates as a host material for the isolation of nuclear wastes.