Structures of CsEuBr3 and its degradation product Cs2EuBr5•10H2O

CsEuBr3, caesium europium tribromide, crystallizes in an orthorhombic perovskite-type structure with an a(-)a(-)c(+) octahedral tilting scheme (GdFeO3 type). CsEuBr3 is unstable in air and one of the degradation products was identified as Cs2EuBr5 . 10H(2)O by single-crystal X-ray analysis and synchrotron powder diffraction. The Eu3+ ions on twofold rotational axes are coordinated by nine water molecules, and each water O atom is linked to two Br atoms by hydrogen bonds. The tricapped trigonal [EuO9] prisms are separated from each other by infinite {Cs2Br5 . H2O} chains; the description Eu(OH2)(9)Cs2Br5(OH2) might therefore be more appropriate. The oxidation of Eu2+ to Eu3+ during the degradation of CsEuBr3 is further confirmed by changes in the magnetic properties from the as-prepared material into the degraded product.