Centric Sc(HPO₃)(H₂PO₃)(H₂O) and Acentric Sc(H₂PO₃)₃: Two Ultraviolet Scandium Phosphite Optical Crystals

Abstract

Exploring ultraviolet (UV) nonlinear-optical (NLO) materials is significant for the conversion of a high-frequency laser. Two scandium phosphites, Sc(HPO 3 )(H 2 PO 3 )(H 2 O) and Sc(H 2 PO 3 ) 3 , were successfully synthesized. Centric Sc(HPO 3 )-(H 2 PO 3 )(H 2 O) exhibits a short UV cutoff edge (<200 nm) and a unique double-layer structure of [Sc 2 (HPO 3 ) 2 (H 2 PO 3 ) 2 (H 2 O) 2 ] ∞ . The acentric Sc(H 2 PO 3 ) 3 exhibits a three-dimensional [Sc(H 2 PO 3 ) 3 ] ∞ structure with a large band gap of 4.05 eV, and it demonstrates a moderately phase-matchable second-harmonic-generation response [0.60 × KDP (KH 2 PO 4 )] at 1064 nm. The crystal structures, optical properties, and theoretical calculations of the two compounds are discussed. This work will promote the exploration of new NLO phosphite materials.

From Pb6(HPO3)(H2PO3)Cl9 to Pb6(HPO3)2Br8(H2O)·H2O: Halogen Regulation to Achieve Inorganic Metal Phosphite Halide Nonlinear Optical Material with Unprecedented Pb-Centered Polyhedral Units

“…As an important branch of nonlinear optical crystals, frequency-doubled crystal materials have been widely studied in the past decades. Researchers have found many excellent NLO crystal materials, such as AgGaS 2 (AGS), ZnGeP 2 (ZGP), LiB 3 O 5 (LBO), KH 2 PO 4 (KDP), KTiOPO 4 (KTP), KBe 2 BO 3 F 2 (KBBF), and β-BaB 2 O 4 (β-BBO). − After decades of research, it is still a hot research direction to explore new crystalline materials with excellent NLO properties and analyze their structure–activity relationships. − …”

“…The phosphite groups exhibit greater polarizability and hyperpolarizability compared to the phosphate groups, while maintaining a similar HOMO–LUMO gap as phosphate groups, making them an excellent unit for constructing NLO crystals . However, most reported NLO phosphites show weak second-harmonic generation (SHG) effects, such as CaHPO 3 (0.31 × KDP), In 2 (HPO 3 ) 3 (H 2 O) (0.17 × KDP), In 2 (HPO 3 ) 3 (H 2 O) 3 ·(H 2 O) (0.20 × KDP), NH 4 In­(HPO 3 ) 2 (0.28 × KDP), Sc­(H 2 PO 3 ) 3 (0.60 × KDP), BaSc 2 (HPO 3 ) 4 (H 2 O) 2 (0.94 × KDP), and ZnHPO 3 ·2H 2 O (0.58 × KDP). − ,− So the introduction of lone-pair metal cations could be a reasonable strategy to explore phosphites with greater SHG effects. Up to now, phosphites containing lone-pair metal cations are mostly centrosymmetric compounds and primarily focus on birefringence.…”