Additive‐Triggered Polar Polymorph Formation: β‐Sc(IO<sub>3</sub>)<sub>3</sub>, a Promising Next‐Generation Mid‐Infrared Nonlinear Optical Material
Chao Wu, Guangfeng Wei, Xingxing Jiang, Qinke Xu, Zheshuai Lin, Zhipeng Huang, Mark G. Humphrey, Chi Zhang
Abstract
Abstract 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 Li 2 CO 3 triggers formation of an NCS precursor at an early nucleation stage, and plays a crucial role in the successful polymorphism transformation. The resultant metastable β‐Sc(IO 3 ) 3 is a promising mid‐infrared NLO crystal, with the strongest second‐harmonic generation responses (2.2×KTiOPO 4 @ 2100 nm, 16×KH 2 PO 4 @ 1064 nm) and the largest optical band gap (4.52 eV) for a rare‐earth iodate, as well as sufficient birefringence (Δ 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.