Multianvil high-pressure/high-temperature preparation, crystal structure, and properties of the new oxoborates Dy4B6O14(OH)2 and Ho4B6O14(OH)2

This paper reports about two new hydrogen-containing rare-earth oxoborates RE4B6O14(OH)(2) (RE= Dy, Ho) synthesized under high-pressure/high-temperature conditions from the corresponding rare-earth oxides, boron oxide, and water using a Walker-type multianvil equipment at 8GPa and 880degreesC. The single crystal structure determination of DY4B6O14(OH)(2) showed: Pbcn, a = 1292.7(2), b = 437.1(2) c = 887.3(2)pm, Z = 2, RI = 0.0190, and wR2 = 0.0349 (all data). The isotypic holmium species revealed: Pbcn, a = 1292.8(2), b = 436.2(2), c = 887.1(2) pm, Z = 2, R1 = 0.0206, and wR2 = 0.0406 (all data). The compounds exhibit a new type of structure, which is built up from layers of condensed BO4-tetrahedra. Between the layers, the rare-earth cations are coordinated by 7 + 2 oxygen atoms. Furthermore, we report about temperature-resolved in situ powder diffraction measurements, DTA/TG, and IR-spectroscopic investigations into RE4B6O14(OH)(2) (RE= Dy, Ho). (C) 2004 Elsevier Inc. All rights reserved.