New europium selenate (Vi) tetrahydrate: Crystal structure and optical properties

New europium selenate tetrahydrate Eu2(SeO4)3·4H2O was prepared by hydrothermal technique for the first time. Its crystal structure was determined by single crystal XRD. Title compound crystallize in triclinic system (Space group P 1¯, a ​= ​6.9287(7)Å, b ​= ​9.2547(10) Å, с ​= ​10.8431(12) Å, α ​= ​95.196(3) °, β ​= ​106.825(3) °, γ ​= ​99.240(3)°, Z ​= ​2). Crystal structure of new compound consists from EuO7 and EuO8 polyhedra connected via SeO42− groups into 3D framework. According to our data Eu2(SeO4)3·4H2O isostructural to Gd2(SeO4)3·4H2O and Er2(SO4)3·4H2O. Eu selenate was studied by IR, UV–Vis spectroscopy, as well as luminescence properties, were examined. The absorption spectrum of the Eu2(SeO4)3⋅4H2O crystal is a superposition of the absorption bands of the Eu3+ ions and the selenate SeO42− groups. The luminescence spectra show transitions of Eu3+ ion energy levels. According to thermal study compound under investigation is stable on air up to 205 ​°C, and at higher temperature become anhydrous Eu2(SeO4)3.