Synthesis and crystal structure of Ba₂Y_0.87(1)Mn_1.71(1)Te₅

We report the structural characterization of a new quaternary telluride, Ba₂Y_0.87(1)Mn_1.71(1)Te₅, which was synthesized by the direct reaction of the elements inside a vacuum-sealed fused-silica tube. The quaternary phase is the first member of the Ba-M-Mn-Te system (M = Sc and Y). The composition and structure of the phase were elucidated using SEM-EDX (scanning electron microscopy-energy dispersive X-ray spectrometry) and single-crystal X-ray diffraction (SCXRD) studies. The title phase is nonstoichiometric and crystallizes in the monoclinic system (space group C2/m) having the refined unit-cell parameters a = 15.1466 (8), b = 4.5782 (3), c = 10.6060 (7) Å and β = 116.956 (2)°, with two formula units (Z = 2). The pseudo-two-dimensional crystal structure of Ba₂Y_0.87(1)Mn_1.71(1)Te₅ consists of distorted YTe₆ octahedra and MnTe₄ tetrahedra as the building blocks of the structure. The YTe₆ octahedra are arranged to form infinite one-dimensional chains by sharing edges along the [010] direction. These chains are further connected to the MnTe₄ tetrahedra along the c axis to create layered two-dimensional polyanionic [Y_0.87(1)Mn_1.71(1)Te₅]^4- units. The stuffing of Ba²⁺ cations in between the layers of [Y_0.87(1)Mn_1.71(1)Te₅]^4- anions brings the charge neutrality of the structure. Each Ba atom in the structure sits at the centre of a distorted monocapped trigonal prism-like polyhedron of seven Te atoms.