Study of structure of Mn 3 Cu 0.5 Ge 0.5 N/Cu composite with nearly zero thermal expansion behavior around room temperature Jun Yan, a Ying Sun, a,⇑ Cong Wang, a,⇑ Lihua Chu, b Zaixing Shi, a Sihao Deng, a Kewen Shi a and Huiqing Lu a a Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191, People’s Republic of China b State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, School of Renewable Energy, North China Electric Power University, Beijing 102206, People’s Republic of China Received 3 March 2014; accepted 7 April 2014 Available online 18 April 2014 An Mn 3 Cu 0.5 Ge 0.5 N/Cu composite was synthesized with 50 wt.% Cu and 50 wt.% Mn 3 Cu 0.5 Ge 0.5 N. The composite has a nearly zero thermal expansion behavior around room temperature and consists of Cu, Mn 3 Cu 0.5 Ge 0.5 N with a small number of MnO particles. There are no chemical reactions between these phases and the thermal expansion property of the composite is stable. Based on the distribution of Cu and Mn 3 Cu 0.5 Ge 0.5 N phases in the composite, we built a structure model to clarify the stability of Mn 3 Cu 0.5 Ge 0.5 N/Cu composite. Ó 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Zero thermal expansion; Composite; Stability; Structure model Zero thermal expansion (ZTE) materials are highly desirable for microelectronics and precision opti- cal devices. In the past 20 years, negative thermal expan- sion (NTE) behavior has been found in many materials, such as the antipreovskite compounds Mn 3 AN(C) (A = Cu, Zn, Ga, Sn) [1–4], PbTiO 3 -based compounds [5], ZrW 2 O 8 compound [6] and NaZn 13 -type La(Fe, Si, Co) 13 compounds [7]. Based on these NTE materials, the fabrication of ZTE materials can be achieved. One method is to adjust the chemical composition to control the coefficient of thermal expansion (CTE) of the NTE materials [7–9]. However, ZTE materials with a single phase are rare. Another way is to combine the NTE materials with positive thermal expansion materials. ZrW 2 O 8 with large NTE has been composited with var- ious materials to produce composites with tunable CTE. For example, ZrW 2 O 8 /Cu [10–12], ZrW 2 O 8 /Al [13], ZrW 2 O 8 /Zr 2 WP 2 O 12 [14], ZrW 2 O 8 /polyimide [15,16] and ZrW 2 O 8 /ZrO 2 [17,18] have been studied. Because the metal Cu, which has high thermal conductivity (397 W m À1 K À1 ) and good ductility, is widely used in the electronics industry, ZrW 2 O 8 /Cu composite was studied to control the high CTE of Cu for microelec- tronic devices [10–12]. However, due to the instability of ZrW 2 O 8 upon heating and the easy chemical reaction between Cu and ZrW 2 O 8 phases [10], it is difficult to control the CTE of the ZrW 2 O 8 /Cu composite [11]. Compared with ZrW 2 O 8 , the antiperovskite NTE materials are stable, and most of them have good ther- mal and electrical conductivity. Our previous report [19] showed that the CTEs of Cu and Mn 3 Cu 0.5 Sn 0.5 N are 1.61 Â 10 À5 and À2.11 Â 10 À5 K À1 (in the tempera- ture range 282–322 K), respectively. The CTE of the composite which consisted of Mn 3 Cu 0.5 Sn 0.5 N (49 wt.%) and Cu (51 wt.%) could reach 4.7 Â 10 À7 K À1 in the temperature range 290–320 K (DT = 30 K) [19]. Takenaka and Takagi [1] reported that Mn 3 Cu 0.5 Ge 0.5 N showed NTE behavior in the tem- perature range 280–365 K, with a CTE of À1.2 Â 10 À5 K À1 . To get a better (nearly zero) CTE composite, here we use Mn 3 Cu 0.5 Ge 0.5 N instead of Mn 3 Cu 0.5 Sn 0.5 N and try to composite Mn 3 Cu 0.5 Ge 0.5 N with Cu metal matrix. In this research, we successfully http://dx.doi.org/10.1016/j.scriptamat.2014.04.010 1359-6462/Ó 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. Tel./fax: +86 1082338346 (C. Wang); e-mail addresses: sunying@buaa.edu.cn; congwang@buaa.edu.cn Available online at www.sciencedirect.com ScienceDirect Scripta Materialia 84–85 (2014) 19–22 www.elsevier.com/locate/scriptamat