K6ACaSc2(B5O10)3 (A = Li, Na, Li0.7Na0.3): Nonlinear-Optical Materials with Short UV Cutoff Edges.

Three new acentric Sc-based borates, K6ACaSc2(B5O10)3 (A = Li, Na, Li0.7Na0.3; space group R32), have been obtained and characterized. They are isostructural, and all exhibit three-dimensional [Sc2(B5O10)3]9- anionic architecture composed of B5O10 clusters and ScO6 octahedra with the alkali- and alkaline-earth-metal cations occupying the cavities and keeping the charge balance. These compounds possess moderate second-harmonic-generation (SHG) responses (∼0.2×β-BaB2O4 at 532 nm and ∼0.4×KH2PO4 at 1064 nm) with phase-matching abilities and importantly display short cutoff edges below 200 nm. Furthermore, the relationship between the crystal structure and the SHG property has also been discussed based on the theoretical calculations.