Two non-centrosymmetric scandium borate nonlinear optical crystals containing the B5O10 anion group

• The non-centrosymmetric borates K 3 ScB 6 O 12 and K 6 NaSrSc 2 B 15 O 30 were found by spontaneous crystallization method. • Both K 3 ScB 6 O 12 and K 6 NaSrSc 2 B 15 O 30 exhibit wide band gaps of 5.75 and 5.92 eV, respectively. • K 6 NaSrSc 2 B 15 O 30 possesses type-I phase matching capability. • The SHG response in K 6 NaSrSc 2 B 15 O 30 is derived mainly from the [B 5 O 10 ] 5− groups and ScO 6 polyhedra. The spontaneous crystallization approach was used to synthesize two non-centrosymmetric scandium borate crystal materials, K 3 ScB 6 O 12 ( 1 ) and K 6 NaSrSc 2 B 15 O 30 ( 2 ), possessing the [B 5 O 10 ] 5− group. Both compounds exhibit wide band gaps of 5.75 and 5.92 eV, respectively. The second harmonic generation (SHG) effects of 1 and 2 are 1.3 and 0.7 times that of the commercial material KH 2 PO 4 (KDP), respectively. According to the Kurtz-Perry approach, 2 demonstrates type-I phase-matchable. First-principles calculations on 2 are done to better understand the link between structure and performance. The calculated results reveal that the discrete arrangement of [B 5 O 10 ] 5− groups and the distorted ScO 6 polyhedra in the structure are mainly responsible for the SHG response of 2 . Furthermore, since 1 and 2 possess short ultraviolet (UV) cut-off edges, they may be applicable as nonlinear optical (NLO) materials in the UV region.