Self-Radiation-Induced Anisotropic Structure Damage in ²⁴⁴Cm-Doped Orthophosphate LuPO₄

We have conducted a series of experiments using laser spectroscopy and analytic electron microscopy (AEM) to study the microscopic effects of radiation damage in single crystals of LuPO4 doped with 244Cm3+ ions. The crystals (body-centered tetragonal, zircon-type structure) were grown in 1980 using a flux method with an initial 244Cm(t1/2 =18.1 y) concentration of ∼1% by weight. The dimensions of the single crystals of Cm3+:LuPO4 are about 0.5×1.0×4.0 mm3. After 17 years, the crystals are no longer transparent. Dark brown to gray straps along the crystal c-axis are observable under an optical microscope. Macroscopic fractures are not obvious on the natural surfaces of the a- and b-planes. However, due to alpha-particle emission of 244Cm, significant microscopic structural damage, including microscopic cavities, has accumulated in this end member of the xenotime minerals