LiMg(IO3)3: an excellent SHG material designed by single-site aliovalent substitution.

An excellent second harmonic generation (SHG) material, LiMg(IO3)3 (LMIO), has been elaborately designed from Li2MIV(IO3)6 (MIV = Ti, Sn, and Ge) by aliovalent substitution of the central MIV cation followed by Wyckoff position exchange. The new structure sustains the ideal-alignment of (IO3)- groups. Importantly, LMIO exhibits an extremely strong SHG effect of roughly 24 × KH2PO4 (KDP) under 1064 nm laser radiation or 1.5 × AgGaS2 (AGS) under 2.05 μm laser radiation, which is larger than that of α-LiIO3 (18 × KDP). The replacement of MIV with Mg2+ without d-d electronic transitions induces an obviously larger band gap (4.34 eV) with a short absorption edge (285 nm). This study shows that single-site aliovalent substitution provides a new synthetic route for designing SHG materials.