Valence Instabilities, Phase Transitions, and Abrupt Lattice Expansion at 5 K in the YbGaGe System
- 23 March 2004
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 126 (14), 4498-4499
- https://doi.org/10.1021/ja049728w
Abstract
The powder synchrotron X-ray diffraction technique was used to study the thermal expansion behavior of the mixed valence layered compound, YbGa1.05Ge0.95 in the temperature range 3−1123 K. A surprising abrupt isosymmetric phase transition, accompanied by a dramatic volume increase (negative thermal expansion), was found at 5 K induced by a sudden Yb valence transition from +(2 + ε) toward +2. At high temperatures, the material undergoes a transformation to a highly disordered structure until it eventually collapses at 1123 K to a structure with isovalent Yb ions and flat Ga/Ge planes (AlB2 type).Keywords
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