High-pressure synthesis and characterization of the rare-earth fluoride borate LaB2O4F

The rare-earth fluoride borate LaB2O4F was synthesized under high-pressure/high-temperature conditions of 1.1 GPa and 1300 C in a Walker-type multianvil apparatus from lanthanum oxide, lanthanum fluoride, and boron oxide. The single-crystal structure determination revealed that LaB2O4F is isotypic to CeB2O4F. The compound crystallizes in the orthorhombic space group Pbca (no. 61) with eight formula units and the lattice parameters a = 8.2493(9), b = 12.6464(6), c = 7.3301(5) A, V = 764.7(2) A3, R1 = 0.0354, and wR2 = 0.0474 (all data). The structure exhibits a 9+1 coordinated lanthanum cation, one threefold coordinated fluoride ion and a chain of corner-sharing [BO3]3- groups. In addition to the IR- and Raman-spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands. (orig.)