Journal of Alloys and Compounds 523 (2012) 75–82 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds jou rn al h om epage: www.elsevier.com/locate/jallcom Homogeneity range and crystal structure of the Ca 2 Mg 5 Zn 13 compound Yi-Nan Zhang a , Dmytro Kevorkov a , Xue Dong Liu b , Florent Bridier c , Patrice Chartrand d , Mamoun Medraj a,∗ a Department of Mechanical Engineering, Concordia University, 1455 de Maisonneuve Blvd. W., Montreal, Quebec, Canada, H3G 1M8 b Center for the Physics of Materials and the Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, Canada, H3A 2T8 c Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Ouest, Montreal, Quebec, Canada, H3C 1K3 d Center for Research in Computational Thermochemistry École Polytechnique (Université de Montréal), Montreal, Quebec, Canada, H3C 3A7 a r t i c l e i n f o Article history: Received 29 October 2011 Received in revised form 7 January 2012 Accepted 12 January 2012 Available online 1 February 2012 Keywords: Intermetallics Phase identification Diffraction Electron microprobe Electron microscopy a b s t r a c t The homogeneity range and crystal structure of the Ca 2 Mg 5 Zn 13 ternary solid solution were determined using SEM, EPMA, EBSD, TEM and X-ray diffraction. This compound has the Ca x Mg y Zn z (8.2 ≤ x ≤ 9.1; 27.1 ≤ y ≤ 31.0; 60.8 ≤ z ≤ 64.7) composition range at 335 ◦ C. The refinement of the XRD patterns was carried out by Rietveld analysis. XRD data showed that this solid solution crystallizes in a hexagonal struc- ture having P6 3 /mmc (194) space group and Sm 3 Mg 13 Zn 30 prototype. The well indexed SAED patterns and Kikuchi diffraction pattern obtained from TEM and EBSD confirmed the crystallographic information obtained by XRD. The atomic coordination spheres and site occupancy were determined. On the basis of the atomic occupancy results and the crystallographic details, a three-sublattice model is proposed for this compound. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The growing need for lightweight, energy-efficient, “green” environmentally friendly products is driving the development of magnesium-based alloys. Such development is mainly realized through a combination of innovative structural design and promis- ing alloys for energy generation, energy storage and transportation [1,2]. The addition of Ca and Zn elements in Mg alloys enhances the strength, castability, creep and corrosion resistance, fracture toughness and age hardening response [3,4]. Recently the biocom- patible glassy alloys with a small amount of Ca have been found in the Ca–Mg–Zn ternary system for the development of biodegrad- able implants [5–8]. These biodegradable metallic implants can be designed to stabilize structure by allowing bone to grow while simultaneously dissolving harmlessly in the body and thereby reducing the burden of surgical intervention [5,7,8]. Hence the Ca–Mg–Zn system is promising as a next-generation material in both transportation and biomedical applications. Understanding the phase equilibria and crystal structure of the ternary intermetal- lic compounds is necessary for further development of alloys in this system and for better understanding of the existing ones. To date, many researchers have studied the Ca 2 Mg 6 Zn 3 compound, ∗ Corresponding author. E-mail address: mmedraj@encs.concordia.ca (M. Medraj). but their results are contradictory [9–14]. More recently, the solu- bility range and crystal structure of a Mg-rich solid solution were determined using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), transmission electron microscopy (TEM) and X-ray diffraction (XRD) by our group [15,16]. In addi- tion, another ternary compound Ca 2 Mg 5 Zn 13 with solubility ranges and its XRD pattern were reported by Clark [10,17], but the crystallographic information was not reported in terms of lattice parameters, space group and structure type. Therefore, the pur- pose of the present research is to investigate the homogeneity range and crystal structure of the Ca 2 Mg 5 Zn 13 ternary compound in the Ca–Mg–Zn system. To be consistent with our previous paper [16], Ca 2 Mg 5 Zn 13 ternary solid solution is addressed as IM3 (intermetal- lic compound) in this paper. 2. Experimental procedure Three solid–solid diffusion couples and four key alloys were prepared. The start- ing materials were Mg (purity 99.98%), Zn (99.99%) ingots and Ca (99%) supplied by Alfa Aesar. The key alloys were prepared in an arc-melting furnace with water- cooled copper crucible in an argon atmosphere using a non-consumable tungsten electrode. Samples were remelted five times to ensure homogeneity. The actual composition of the samples was determined by inductively coupled plasma-mass spectrometry (ICP-MS). The difference between nominal compositions and actual compositions is below 3 at.%. To prepare solid–solid diffusion couples, the contact- ing surfaces were ground down to 1200 grit SiC paper and polished using 1 m water-based diamond suspension with 99% pure ethanol as a lubricant. Two end members were carefully pressed, clamped with a steel ring, placed in a Ta container and sealed in a quartz tube. The tube was filled with argon to avoid the reaction 0925-8388/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2012.01.068