1. Synthesis, crystal structures and photoluminescence properties of new oxyborates, Mg5NbO3(BO3)3 and Mg5TaO3(BO3)3, with novel warwickite-type superstructures
- Author
-
Hisanori Yamane and Tetsuya Kawano
- Subjects
Flux method ,Photoluminescence ,Materials science ,Crystal structure ,Type (model theory) ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Crystallography ,Materials Chemistry ,Ceramics and Composites ,Orthorhombic crystal system ,Crystallite ,Physical and Theoretical Chemistry ,Isostructural ,Natural bond orbital - Abstract
Single crystals of new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were prepared at 1370 deg. C in air using B{sub 2}O{sub 3} as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3} to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) A, b=9.4344(2) A, c=9.3379(3) A and Z=4 for Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and a=9.3702(3) A, b=9.4415(3) A, c=9.3301(2) A and Z=4 for Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}. The crystal structures of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3} are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} prepared by solid state reaction at 1200 deg. C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature. - Graphical abstract: Single crystals of new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were synthesized by a self flux method. They crystallize in novel warwickite-type superstructuresmore » having ordered arrangements of Mg and Nb/Ta atoms. Highlights: > Single crystals of two new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were prepared using B{sub 2}O{sub 3} as a flux. > Both oxyborates crystallize in isotypic novel warwickite-type superstructures with seven-fold coordinated Nb/Ta atoms. > Polycrystalline sample of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} was prepared by solid state reaction. > Polycrystalline Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} exhibits broad blue-to-green emission with a peak wavelength of 470 nm under 270-nm excitation.« less
- Published
- 2011