Mixed-valent ternary sulfide Eu5In5S13

Abstract

Europium indium sulfide, Eu₅In₅S₁₃, was prepared at 1000 °C. Single-crystal X-ray diffraction reveals that it adopts the Pb₄In₂Bi₄S₁₃-type structure (orthorhombic, space group Pbam, a = 20.722(2) Å, b = 25.911(3) Å, c = 3.9883(4) Å, Z = 4), built up from Eu-centred bicapped trigonal prisms and In-centred tetrahedra and octahedra; two metal sites are disordered with Eu and In atoms in octahedral coordination. Magnetic susceptibility measurements, electron paramagnetic resonance spectroscopy, and ¹⁵¹Eu Mössbauer spectroscopy indicate the coexistence of magnetic Eu²⁺ and non-magnetic Eu³⁺. The optical diffuse reflectance spectrum shows a 1.5 eV band gap, which is a direct one as indicated by electronic structure calculations.