E Gratz et al 1996 J. Phys.: Condens. Matter 8 8351 doi:10.1088/0953-8984/8/43/026
Temperature- and pressure-induced structural transitions in rare-earth-deficient 
(R = Y, Sm, Gd, Tb) Laves phases
E Gratz
, A Kottar, A Lindbaum, M Mantler
, M Latroche§, V Paul-Boncour§, M Acet||, Cl Barner||, W B Holzapfel¶, V Pacheco+ and K Yvon+
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.
- PACS
-
64.70.K- Solid–solid transitions
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
65.40.De Thermal expansion; thermomechanical effects
61.72.J- Point defects and defect clusters
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
- Subjects
- Dates
-
Issue 43 (21 October 1996)
Received 21 June 1996, in final form 12 August 1996
-
Temperature- and pressure-induced structural transitions in rare-earth-deficient (R = Y, Sm, Gd, Tb) Laves phases
E Gratz et al 1996 J. Phys.: Condens. Matter 8 8351
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