High-Pressure Preparation, Crystal Structure, and Properties of α-(RE)2B4O9 (RE=Eu, Gd, Tb, Dy): Oxoborates Displaying a New Type of Structure with Edge-Sharing BO4 Tetrahedra
✍ Scribed by Holger Emme; Hubert Huppertz
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 322 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
High‐pressure/high‐temperature conditions of 10 GPa and 1150 °C were used to synthesize the new rare‐earth oxoborates α‐(RE)~2~B~4~O~9~ (RE=Eu, Gd, Tb, Dy) in a Walker‐type multianvil apparatus. Single‐crystal X‐ray structure determination of α‐(RE)~2~B~4~O~9~ (RE=Eu, Gd, Tb) revealed: __C__2/c, Z=20, α‐Eu~2~B~4~O~9~: a=2547.9(5), b=444.3(1), c=2493.8(5) pm, β=99.82(3)°, __R__1=0.0277, __wR__2=0.0693 (all data); α‐Gd~2~B~4~O~9~: a=2539.0(1), b=443.3(1), c=2490.8(1) pm, β=99.88(1)°, __R__1=0.0457, __wR__2=0.0643 (all data); α‐Tb~2~B~4~O~9~: a=2529.4(1), b=441.6(1), c=2484.3(1) pm, β=99.88(1)°, __R__1=0.0474, __wR__2=0.0543 (all data). The isotypic compounds exhibit a new type of structure that is built up of BO~4~ tetrahedra to form a network that incorporates the rare‐earth cations. The most important feature is the existence of the new structural motif of edge‐sharing BO~4~ tetrahedra next to the known motif of corner‐sharing BO~4~ tetrahedra, which is realized in the presented compounds α‐(RE)~2~B~4~O~9~ (RE=Eu, Gd, Tb, Dy) for the second time. Furthermore, we report the temperature‐resolved in‐situ powder‐diffraction measurements, DTA, IR/Raman spectroscopic investigations, and magnetic properties of the new compounds.