High-Pressure Preparation, Crystal Structure, and Properties of RE4B6O15 (RE = Dy, Ho) with an Extension of the “Fundamental Building Block”-Descriptors

Abstract

High-pressure/high-temperature conditions of 8 GPa and 1000°C were used to synthesize the new rare earth oxoborates RE4B6O15 (RE = Dy, Ho) in a Walker-type multianvil apparatus. The single crystal X-ray structure determination of Ho4B6O15 revealed the following data: C2/c, a = 1164.1(1), b = 436.7(1), c = 1882.5(1) pm, β = 96.71(1)°, Z = 4, R1 = 0.0291, wR2 = 0.0505 (all data). The two isotypic compounds exhibit a new structure type built up from corrugated layers of BO4 tetrahedra. In contrast to all known oxoborates the linking of the BO4 tetrahedra is partially realized via common edges. Regarding the “fundamental building block”-concept, we introduce a new descriptor “ ” for edge-sharing BO4 tetrahedra. Temperature-resolved in situ powder diffraction measurements and IR/Raman-spectroscopic investigations on Dy4B6O15 are also reported.