Sodalite-like rare-earth carbonates: a study of structural transformation and diluted magnetism

Abstract

A series of novel rare earth carbonates, RE₃(OH)₆(CO₃)Cl (RE = Dy, Er, Y), with sodalite-like (SOD-like) zeolite topologies have been successfully synthesized by introducing an appropriate amount of CO₃²⁻ from NaCO₃ or atmospheric carbon dioxide as a template. Single-crystal X-ray diffraction reveals that the structure consists of the RE₃(OH)₆³⁺ cationic framework with a SOD-like topology built from vertex-sharing [RE₄(μ₃-OH)₄] cubes. The CO₃²⁻ anions seal the 6-ring opening and Cl⁻ anions situated in the channels to achieve charge balance. After calcination at 370 °C, the compound RE₃(OH)₆(CO₃)Cl in situ transforms into a new phase formulated as RE₃O₄Cl. Interestingly, the structure of RE₃O₄Cl represents a new SOD-like open framework, associated with the removal of the CO₃²⁻ from RE₃(OH)₆(CO₃)Cl. The samples are characterized by thermogravimetric analysis (TGA), elemental analysis, X-ray photoelectron spectroscopy and magnetic studies. Furthermore, single-molecule magnet behaviours can be observed for the diluted samples of Dy_0.0068Y_2.9932(OH)₆(CO₃)Cl and Dy_0.0068Y_2.9932O₄Cl with a Dy/Y molar ratio of up to 1/440 as well as Er_0.19Y_2.81(OH)₆(CO₃)Cl with an Er/Y ratio of 1/15, showing dominant single-ion effects.