Synthesis, characterization and thermal behaviour of new copper and rare-earth metal tungstates |
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Authors: | E. Tomaszewicz J. Typek S. M. Kaczmarek |
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Affiliation: | 1. Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Al. Piastow 42, 71-065, Szczecin, Poland 2. Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310, Szczecin, Poland
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Abstract: | Three series of new copper and rare-earth metal tungstates with the formulas: CuRE 2W2O10 (RE = Nd, Sm, Eu) and Cu3 RE 2W4O18 (RE = Sm, Eu or RE = Dy, Ho, Er) were synthesized by the solid-state reaction method. The CuRE 2W2O10 and Cu3 RE 2W4O18 (RE = Dy, Ho, Er) compounds crystallize in the monoclinic system. The Cu3 RE 2W4O18 phases with the large rare-earth ions crystallize in the triclinic system. All obtained compounds melt incongruently below 1273 K. The anion lattice of the Cu3 RE 2W4O18 phases is built from isolated groups of octahedra (W4O16)8?, while CuRE 2W2O10 from WO6 octahedra forming structural elements [(W2O9)6?]∞. The EPR spectra of analyzed compounds consisted of an intense line originating generally from the rare-earth ions and a weak, narrow line from Cu2+ separate centers appearing only on the surface of the grains. The absence of bulk copper in the EPR spectrum is probably due to a very short relaxation time of the Cu2+ subsystem. |
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