High-Pressure Synthesis and Characterization of the Actinide Borate Phosphate U₂[BO₄][PO₄]

A new actinide borate phosphate, U₂[BO₄][PO₄], was synthesized in a Walker-type multianvil apparatus at 12.5 GPa and 1000 °C. The crystal structure was determined from single-crystal X-ray diffraction data collected at room temperature. U₂[BO₄][PO₄] crystallizes in the monoclinic space group P2₁/c with four formula units per unit cell and the lattice parameters a = 854.6(2), b = 775.3(2), c = 816.3(2) pm, and β = 102.52(3)°. The structure consists of double layers of linked uranium-oxygen polyhedra parallel to [100]. The borate tetrahedra are located between the uranium-oxygen layers inside the double layer. The phosphate groups link the double layers.