L Journal of Alloys and Compounds 311 (2000) 234–237 www.elsevier.com / locate / jallcom Neutron diffraction study of the location of deuterium in the deuterium-stabilized ZrTi D phase 2 3.83 a, b b ,1 b a * A.V. Skripov , T.J. Udovic , Q. Huang , J.C. Cook ,V.N. Kozhanov a Institute of Metal Physics, Urals Branch of the Academy of Sciences, Ekaterinburg 620219, Russia b NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA Received 31 March 2000; accepted 28 June 2000 Abstract The location of D atoms in the deuterium-stabilized ZrTi D phase with C15-type host lattice has been studied by neutron diffraction 2 3.83 ] in the temperature range 11–300 K. It is found that D atoms occupy two types of sites of the space group Fd3m: 32e (ZrTi ) and 96g 3 (Zr Ti ). Most of the deuterium atoms are located in 32e sites. The occupancy of these sites is found to increase from 0.81 at 300 K to 2 2 0.94 at 11 K. Thus, as the temperature decreases, the ZrTi –D system approaches the fully ordered state with the completely occupied 2 sublattice of 32e sites.  2000 Elsevier Science S.A. All rights reserved. Keywords: Metal hydrides; Laves phases; Neutron powder diffraction 1. Introduction wide range of hydrogen content [7] have shown that, for the C15-type ZrTi H phase, a single-phase state at room 2 x The hydrogen-stabilized ZrTi H (D ) phase discovered temperature is retained up to x 5 4.7. Since the complete 2 x x by Miron et al. [1] is an interesting example of hydrogen- filling of the e-site sublattice corresponds to x 5 4, one induced ordering in alloys. Zr and Ti form only disordered may expect g sites to be partially occupied by hydrogen, at solid solutions with the hexagonal close-packed (h.c.p.) least for x . 4. (2) Quasielastic neutron scattering mea- lattice. However, the absorption of hydrogen by the surements [8] have revealed that a fraction of hydrogen disordered h.c.p. alloy Zr Ti results in the formation atoms in ZrTi H participate in the fast localized hopping 0.33 0.67 2 3.9 of the ZrTi H (D ) phase (3 # x # 4) with an ordered within the hexagons formed by g sites. (3) The hydrogen 2 x x cubic C15-type host lattice [1,2]. Recently, a similar vibrational spectrum of ZrTi H measured by inelastic 2 3.6 hydrogen-stabilized phase with a C15-type host lattice has neutron scattering [9] contains additional weak peaks at been found in the HfTi –H(D) system [3,4]. 110 meVand 145 meV; these peaks may result [10] from a 2 Hydrogen atoms in C15-type hydrides AB H (D ) are partial occupancy of g sites in this compound. (4) Neutron 2 x x known to occupy two types of tetrahedral interstitial sites: diffraction measurements on the closely related system 32e (AB ) and 96g (A B ). In most of the studied C15 HfTi D [4] have shown that, at room temperature, about 3 2 2 2 4 hydrides, H(D) atoms occupy only g sites at low hydrogen 3/4 of all D atoms occupy e sites, the rest of D atoms concentrations; e sites start to be filled above x ¯ 3 [5,6]. being in g sites. It should also be noted that, in the early On the basis of neutron diffraction measurements, H(D) diffraction work on ZrTi D [1], the data treatment was 2 x atoms in C15-type ZrTi H (D ) have been reported [1] to semi-quantitative (the diffraction profile was not refined), 2 x x occupy only e sites. However, a number of recent results and therefore the resulting site occupancies might not be make this conclusion questionable. (1) X-ray diffraction quite reliable. studies of the phase diagram of the ZrTi –H system over a The aim of the present work is to study the location of 2 deuterium in the deuterium-stabilized ZrTi D phase and 2 x the changes in deuterium distribution with temperature. We *Corresponding author. have performed high-resolution neutron diffraction mea- E-mail address: skripov@imp.uran.ru (A.V. Skripov). 1 surements on a powdered ZrTi D sample in the tem- Also at the Department of Materials and Nuclear Engineering, 2 3.83 University of Maryland, College Park, MD 20742, USA. perature range 11–300 K. The results are analysed to 0925-8388 / 00 / $ – see front matter  2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388(00)01108-7