Additive-Triggered Polar Polymorph Formation: β-Sc(IO3)3, a Promising Next-Generation Mid-Infrared Nonlinear Optical Material

Noncentrosymmetric (NCS) solids have attracted interest for their potential in ferroelectric, piezoelectric, and nonlinear optical (NLO) devices, but their synthesis remains a major challenge. In this study, the additive Li2CO3 triggers formation of an NCS precursor at an early nucleation stage, and plays a crucial role in the successful polymorphism transformation. The resultant metastable beta-Sc(IO3)(3) is a promising mid-infrared NLO crystal, with the strongest second-harmonic generation responses (2.2xKTiOPO(4) @ 2100 nm, 16xKH(2)PO(4) @ 1064 nm) and the largest optical band gap (4.52 eV) for a rare-earth iodate, as well as sufficient birefringence (Delta n=0.219 @ 546 nm) for type I phase-matching, and wide optical transparency, which are induced by optimal alignment of the iodate anions. This study reveals the key role of additives in the growth of polar NCS solids, a discovery with implications for the strategic design of new NCS polymorphism materials with exceptional NLO properties.

Automated summary

The synthesis of noncentrosymmetric (NCS) solids has always been a major challenge. This study demonstrates that the addition of Li2CO3 triggers the formation of an NCS precursor and plays a crucial role in the successful polymorphism transformation. The resulting β-Sc(IO3)3 crystal exhibits promising potential for mid-infrared NLO devices, with strong second-harmonic generation responses, a large optical band gap, sufficient birefringence, and wide optical transparency, which are induced by the optimal alignment of iodate anions. This study reveals the importance of additives in the growth of polar NCS solids and has implications for the strategic design of new NCS polymorphism materials with exceptional NLO properties.