Li 7 SrScB 12 O 24 and Li 7 Ba 0.6 Ca 0.4 ScB 12 O 24 : two new quaternary rare-earth borates with short UV cutoff edges

Two new quaternary rare-earth borates, Li 7 M II ScB 12 O 24 (M II = Sr, Ba 0.6 Ca 0.4 ), crystallizing in the centrosymmetric space group R 3̄ were synthesized by a high-temperature solution method and characterized. They are isostructural and exhibit a three-dimensional anionic [ScB 12 O 24 ] 9− framework composed of B 6 O 14 groups and ScO 6 octahedra with alkali- and alkaline-earth metal cations occupying the cavities and keeping the charge balance. The UV-Vis-NIR diffuse reflectance spectrum shows that the cutoff edge of Li 7 SrScB 12 O 24 is less than 200 nm, which indicates its potential application in the deep UV region. Li 7 M II ScB 12 O 24 (M II = Sr, Ba 0.6 Ca 0.4 ) will become a new type of rare-earth borates that have a deep-UV cutoff edge (≤200 nm). Furthermore, infrared spectroscopy and thermal analysis were carried out and the results were analyzed.