Struvite-type AMgPO4•6H2O (A = NH4, K): Two Natural Deep-Ultraviolet Transparent Nonlinear Optical Crystals

Deep-ultraviolet (DUV) nonlinear optical (NLO) materials play vital roles in diverse fields. Unfortunately, only the KBe2BO3F2 crystal has found commercial applications so far. Therefore, the discovery of new DUV NLO crystals is still urgent. As we all know, digging into the properties of existing crystals is also an effective way to obtain new NLO crystals. Herein, two natural asymmetric orthophosphates AMgPO(4)center dot 6H(2)O (A = NH4, K) are proposed. Although their structures and some properties such as infrared spectra, thermal properties, and dielectric properties have been previously characterized, their NLO properties have not been reported. Thus, in this work, these two natural DUV transparent orthophosphates NH4MgPO4 center dot 6H(2)O (NMP) and KMgPO4 center dot 6H(2)O (KIVIP) were successfully acquired by a simple slow evaporation method. The single-crystal X-ray diffraction data indicate that NMP and KMP are isomorphic and that both belong to the Pmn2(1) space group of the orthorhombic system. Remarkably, NMP and KMP possess short cutoff edges below 190 nm, and their second-harmonic generation (SHG) efficiencies are 0.62 and 0.80 times that of KH2PO4 (KDP), respectively; furthermore, they can achieve type-I phase matching at 1064 nm.

Automated summary

In this study, two natural deep-ultraviolet (DUV) transparent orthophosphates NH4MgPO4 center dot 6H(2)O (NMP) and KMgPO4 center dot 6H(2)O (KIVIP) were successfully obtained by a simple slow evaporation method. The single-crystal X-ray diffraction data showed that NMP and KMP are isomorphic and belong to the Pmn2(1) space group of the orthorhombic system. Remarkably, these crystals exhibit short cutoff edges below 190 nm and second-harmonic generation (SHG) efficiencies that are 0.62 and 0.80 times that of KH2PO4 (KDP), respectively, with type-I phase matching achieved at 1064 nm.