title: Crystal structure of the low-temperature phase of beta Cu1.75Se analysed by electron diffraction
abstract: The beta phase of Cu1.75Se has an anti-fluorite structure, where one in eight tetrahedral copper sites are vacant. Powder X-ray diffraction measurements on Cu1.75Se showed that the beta phase transformed to a two-phase mixture of (alpha + beta) at approximately 250 K, and then the beta phase changed to a new phase at approximately 180 K. Powder X-ray and electron diffraction measurements revealed that the low-temperature phase of the beta phase has a superstructure of (2alpha(fcc) x 2alpha(fcc) x 2alpha(fcc)) type, where alpha(fcc) is the lattice parameter of the original beta phase. The superstructure was interpreted to originate from the ordering copper vacancies. The new phase was referred to as the beta' phase.
authors.affiliation: Faculty of Science, Okayama University of Science, Japan.
authors.initials: Y
authors.lastname: Okada
authors.initials: T
authors.lastname: Ohtani
authors.initials: Y
authors.lastname: Yokota
authors.initials: Y
authors.lastname: Tachibana
authors.initials: K
authors.lastname: Morishige