Crystallization Improvements in Studtite by Vapor Diffusion Synthesis

Studtite is a common nuclear fuel cycle material that has been the focus of considerable research due to its role as a uranium ore concentrate. In a laboratory setting, studtite is commonly synthesized via the addition of liquid-phase hydrogen peroxide to an aqueous uranyl nitrate solution. The product produced from this process is a very fine, pale-yellow powder with crystals of ∼0.1 μm in their largest dimension. In this work, we implement a small modification to this process by introducing hydrogen peroxide in the vapor phase. This change eliminates mechanical agitation and increases crystallization time, resulting in crystals measuring 10-20 μm. Due to the thermal decomposition mechanism of studtite, this increased crystal size is preserved through heating, leading to large crystals of both metastudtite and α-UO₃. Raman spectroscopy and powder X-ray diffraction are used to determine crystallographic information and structures, and scanning electron microscopy is used to visually compare samples produced via the traditional method and our vapor diffusion method. The samples obtained using this technique open the door to future investigations in which large single crystals are required for full structural characterization.