Preparation and characterization of a europium(II) bromide-chloride phase EuBr1.5Cl0.5

A divalent europium chloride-bromide phase, EuBr_1.56(7)Cl_0.46(2) has been prepared and identified on the basis of analytical, X-ray powder diffraction and single-crystal data. Although the phase is considered isostructural with EuCl₂ (PbCl₂ structure type, a = 0.9230 (5), b = 0.7890 (4), c = 0.4613 (3) nm, space group Pbnm), the single-crystal data indicate long-range order in the form of a superstructure which doubles the b parameter. In the pseudocell the square pyramidal anion sites are occupied principally by bromide ions, the tetrahedral sites almost equally by bromide and chlorine ions. Structural details and the long-range order are discussed. Evidence is presented for the existence of another europium(II) mixed halide phase, EuBr_1.8(2)Cl_0.16(2).