Three mixed-valent selenium compounds: Cd₃(SeO₃)₂(SeO₄), Hg₃(SeO₃)₂(SeO₄) and Pb₂(SeO₃) (SeO₄) were successfully synthesized by hydrothermal methods. Among these three compounds, Cd₃(SeO₃)₂(SeO₄) and Hg₃(SeO₃)₂(SeO₄) are isostructural and crystalize in the noncentrosymmetric (NCS) polar space group P2₁. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate that Cd₃(SeO₃)₂(SeO₄) and Hg₃(SeO₃)₂(SeO₄) exhibit SHG intensities of approximately 0.6 and 0.8 times of KH₂PO₄ (KDP), respectively. Pb₂(SeO₃) (SeO₄) is centrosymmetric (CS) and crystalizes in the space group Pnma. Pb₂(SeO₃) (SeO₄) exhibits a 3D framework composed of chains of edge-sharing [PbO₆] octahedra linked to [SeO₃] and [SeO₄] groups. M₃(SeO₃)₂(SeO₄) (M = Cd, Hg) also exhibits a 3D structure consisting of layers of [MO₈], [MO₆] and [SeO₃] polyhedra connected by [SeO₄] groups. For all of the reported compounds, infrared spectroscopy, UV–vis diffuse reflectance spectroscopy and thermogravimetric measurements were performed.

通过水热法成功合成了三种混合价硒化合物：Cd ₃（SeO ₃）₂（SeO ₄），Hg ₃（SeO ₃）₂（SeO ₄）和Pb ₂（SeO ₃）（SeO ₄）。在这三种化合物中，Cd ₃（SeO ₃）₂（SeO ₄）和Hg ₃（SeO ₃）₂（SeO ₄）是同构的，并且在非中心对称（NCS）极性空间群P 2 _1中结晶。。使用1064 nm辐射的粉末二次谐波生成（SHG）测量表明，Cd ₃（SeO ₃）₂（SeO ₄）和Hg ₃（SeO ₃）₂（SeO ₄）的SHG强度约为KH _2的0.6和0.8倍PO ₄（KDP）分别。Pb ₂（SeO ₃）（SeO ₄）是中心对称的（CS），在空间群Pnma中结晶。Pb ₂（SeO ₃）（SeO ₄）展示了一个由边缘共享[PbO ₆]八面体链接到[SeO ₃ ]和[SeO ₄ ]组。M ₃（SeO ₃）₂（SeO ₄）（M = Cd，Hg）也表现出由[MO ₈ ]，[MO ₆ ]和[SeO ₃ ]多面体层构成的3D结构，这些层通过[SeO ₄ ]基连接。对于所有报告的化合物，均进行了红外光谱，紫外可见漫反射光谱和热重测量。