Crystal structure of the high-Tc superconductor HoSr2Cu2.7Mo0.3O7.54 by joint time-of-flight neutron/x-ray rietveld refinement

The ambient-pressure synthesis, crystal structure, and some properties of HoSr2Cu2.7Mo0.3O7.54 are described. HoSr2 Cu2.7Mo0.3O7.54 crystallizes as the tetragonal modification of the YBa2Cu3O7-δ (123) high-Tc superconductor structure, and exhibits a superconducting transition temperature of ∼30 K. The Cu/Mo cation distribution in HoSr2Cu2.7Mo0.3O7.54 was established by means of a joint time-of-flight neutron/X-ray Rietveld refinement: The molybdenum ions substitute for copper at both the open-quotes chainclose quotes [Cu(1)] and square-pyramidal [Cu(2)] sites in roughly equal proportion. The chain layers [atoms Cu/Mo(1) and O(1)] show considerable static disorder in this material. Crystal data: HoSr2Cu2.7Mo0.3O7.54, Mr = 660.51, tetragonal, space group P4/mmm (no. 123), a = 3.83107(6) angstrom, c = 11.5347(3) angstrom, V = 169.296(8) angstrom 3, Z = 1, Rp = 4.21%, Rwp = 5.08%, and χ2 = 2.45