Temperature- and pressure-induced structural transitions in rare-earth-deficient (R = Y, Sm, Gd, Tb) Laves phases
| Autor: | A Lindbaum, A Kottar, M Acet, Cl Barner, M Mantler, Michel Latroche, V Pacheco, E Gratz, W B Holzapfel, Valérie Paul-Boncour, K Yvon |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Journal of Physics: Condensed Matter. 8:8351-8361 |
| ISSN: | 1361-648X 0953-8984 |
| DOI: | 10.1088/0953-8984/8/43/026 |
| Popis: | Electrical resistivity, thermal expansion, and temperature-dependent x-ray diffraction measurements on compounds give mutually consistent evidence for structural phase transitions at 740 K, 550 K, 600 K, and 450 K respectively for R = Y, Sm, Gd, Tb; 0 < x < 0.05. Arguments are given as to why most of the rare-earth - nickel compounds with the 1:2 ratio do not crystallize in the simple cubic Laves phase (C15 type) but show a superstructure of the cubic Laves phase at room temperature and at ambient pressure. This superstructure with the space group and a doubled cell parameter is characterized by ordered vacancies on the R sites. It is shown that the observed structural instabilities result in transitions to the cubic Laves phase (space group ), however with disordered vacancies at high temperatures. High-pressure x-ray powder diffraction experiments show that the phase transition in shifts down to room temperature for a pressure of 27 GPa. |
| Databáze: | OpenAIRE |
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