Synthesis and Crystal Structure of the Praseodymium Orthoborate λ-PrBO3

The praseodymium orthoborate lambda-PrBO3 was synthesized from Pr6O11, B2O3, and PrF3 under high-pressure / high-temperature conditions of 3 GPa and 800 degrees C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature. The title compound crystallizes in the orthorhombic aragonite-type structure, space group Pnma, with the lattice parameters a = 577.1(2), b = 506.7(2), c = 813.3(2) pm, and V = 0.2378(2) nm(3), with R-1 = 0.0400 and wR(2) = 0.0495 (all data). Within the trigonal-planar BO3 groups, the average B-O distance is 137.2 pm. The praseodymium atoms are ninefold coordinated by oxygen atoms.