Journal of Alloys and Compounds 425 (2006) 123–128 X-ray diffraction study of the structure and thermal parameters of the ternary Au–Ag–Pd alloys A.B. Ziya a,b,∗ , K. Ohshima b a Department of Physics, Bahauddin Zakariya University, Multan-60800, Pakistan b Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573, Japan Received 10 October 2005; received in revised form 3 January 2006; accepted 4 January 2006 Available online 14 February 2006 Abstract In situ X-ray diffraction experiments were performed on six samples of the ternary Au–Ag–Pd alloys (with A1 structure) having different compositions using a Cu-target. The integrated intensity data obtained in the temperature range of 373–1200 K was utilized to determine the lattice parameters and the thermal parameters like Einstein’s temperatures (Θ E ), the mean-square amplitudes ( u 2 (T )) and the coefficients of thermal expansion with a high accuracy. The lattice parameter showed a small negative deviation from the Vegard’s rule. It is also found that the mean- square amplitudes are independent of the static displacements. The mean-square amplitudes of vibration and the linear thermal expansion follow the classical Gr ¨ uneisen relationship in these alloys. © 2006 Elsevier B.V. All rights reserved. Keywords: Alloys; Structure; Thermal properties; X-ray diffraction 1. Introduction The Au(Ag)-based multicomponent alloys have been investi- gated for use in various technological applications, e.g. biomed- ical applications, electrical contacts and jewellery, etc. [1]. They are considered suitable for such applications in industry owing to their low electrical resistivity, relatively non-toxic nature and corrosion resistance. Pd is a whitening agent and a significant constituent of the Pd-white golds based on these noble metals. The binary Au–Ag, Au–Pd and Ag–Pd alloys form a continu- ous series of solid solutions over a wide range of composition and temperature. The ternary alloys of Au, Ag and Pd are thus expected to form single phase solid solutions at all temperatures below the solidus [2]. Since various properties of these alloys depend on the microstructural conditions, the information obtained on their structure and thermal properties can, therefore, be used to design alloys and heat treatments based on such knowledge. One of the important tasks in crystallography is the determination of ∗ Corresponding author. Tel.: +92 61 4745263; fax: +92 61 9210068. E-mail address: amer ziya@yahoo.com (A.B. Ziya). the mean-square amplitudes of vibration because such an accu- rate knowledge is essential for the understanding of the crystal structures or the refinement of known crystal structures. The expansion and contraction of alloys as a result of temperature change is not only of immense theoretical interest but of fun- damental importance in many industrial applications [3]. The effect of this phenomenon on alloy specimens is expressed through a coefficient of linear thermal expansion. 1 The sci- entific understanding and technological importance of ther- mal expansion of the alloys has lead to the measurement of this property for various materials [3], e.g. the binary Au–Ag [4], Au–Pd [4–7] and Ag–Pd [4,8–9] alloys, but the experi- mental data on the ternary Au–Ag–Pd alloys is rather limited [3–4]. Naidu and Houska in the pioneer work, studied the variations of the structure of highly deformed fillings of the Au–Ag–Pd alloys in order to explain the hardening mechanisms [3–4]. However, they have reported the values of the lattice parameter and the coefficient of thermal expansion on a few composi- 1 Denoted by α and defined as (l/l 0 )/T, where l 0 is the length of the spec- imen, l/l 0 the relative elongation and T the change in temperature at the reference temperature. 0925-8388/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2006.01.023