title: Structural study of a series of layered rare-earth hydroxide sulfates.
abstract: We report structure analysis of a new family of rare-earth hydroxides Ln(2)(OH)(4)SO(4)·2H(2)O (Ln = Pr, Nd, Sm, Eu, Gd, Tb) from synchrotron X-ray and electron diffraction data. Rietveld profile analysis revealed that all members were isostructural and crystallized in a face-centered monoclinic system A2/m (No. 12), in which the monoclinic angles were approximately equal to the right angle, varying from 90.387(1)° for Pr sample to 90.0718(3)° for Tb sample. The structure consisted of LnO(9) polyhedra connected by μ(3)-hydroxyl groups and μ(2)-water molecules, forming a corrugated two-dimensional layer, which was pillared by bidentated sulfate ions. This series of compounds had a supercell a' = 2a, b' = 2b because of the local orientation ordering of SO(4)(2-). Structural features along the series, such as unit-cell parameters and average Ln-O distances, represented a progressive contraction associated with the shrinking radius of the lanthanide cations from Pr to Tb.
authors.affiliation: International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Fengxia
authors.initials: F
authors.lastname: Geng
authors.forename: Renzhi
authors.initials: R
authors.lastname: Ma
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Matsushita
authors.forename: Jianbo
authors.initials: J
authors.lastname: Liang
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Michiue
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Sasaki