High-pressure synthesis and characterization of the fluoride borate Tmi(BO_3)_2F_9

摘要

The rare earth fluoride borate Tm_5(BO_3) _2F_9 was synthesized from Tm2O3, B2O3, and TmF3 under high-pressure/high-temperature conditions of 5 GPa and 900 °C in a Walker-type multianvil apparatus. The single-crystal structure determination revealed that Tm_5(BO_3)_2F_9 is isotypic to the compounds RE_5(BO_3)_2F _9 (RE = Er,Yb). Tm_5(BO_3)_2F _9 crystallizes in the space group C2/c (Z = 4) with the parameters a = 2030.9(4), b = 606.2(2), c = 822.6(2) pm, β = 100.5(1)?, V = 995.7(3) ?3, R1 = 0.0341, and wR2 = 0.0724 (all data). The structure is composed of isolated BO3 groups, ninefold coordinated thulium cations, and fluoride anions. Infrared and Raman spectroscopic data of Tm_5(BO_3) _2F_9 are compared to the data of RE_5(BO _3)_2F_9 (RE = Er, Yb).