High-pressure synthesis and characterization of the rare-earth fluoride borate LaB_2O_4F

摘要

The rare-earth fluoride borate LaB_2O_4F was synthesized under high-pressure=high-temperature conditions of 1.1 GPa and 1300 °C in aWalker-type multianvil apparatus from lanthanum oxide, lanthanum fluoride, and boron oxide. The single-crystal structure determination revealed that LaB_2O_4F is isotypic to CeB_2O_4F. 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) ?, V = 764.7(2) ?~3, R_1 = 0.0354, and wR_2 = 0.0474 (all data). The structure exhibits a 9+1 coordinated lanthanum cation, one threefold coordinated fluoride ion and a chain of corner-sharing [BO_3]~(3-) groups. In addition to the IR-and Raman-spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.