High-pressure synthesis and crystal structure of the new holmium oxoborate Ho_(31)O_(27)(BO_3)_3(BO_4)_6

摘要

The new rare-earth oxoborate Ho_(31)O_(27)(BO_3)_3(BO_4)_6 was synthesized in a Walker-type module under high-pressure/high-temperature conditions of 7.5-11.5 GPa and 1200 °C. The compound crystallizes in the space group R3 (no. 148) with the lattice parameters a = 2657.9(4) pm and c = 1146.9(2) pm (Z = 6). The structure exhibits 11 different Ho cations next to three and six independent BO_3- and BO_4-groups, respectively. With an elemental ratio of Ho:B = 3.44 (31:9), Ho_(31)O_(27)(BO_3)_3(BO_4)_6 represents the rare-earth richest rare-earth oxoborate known to this day.