A solvothermal reaction route for the synthesis of CuFeS 2 ultrafine powder
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A solvothermal reaction route for the synthesis of CuFeS2 ultrafine powder Junqing Hu, Qingyi Lu, Kaibin Tang,a) Yitai Qian,a) Guien Zhou, and Xianming Liu Department of Chemistry and Structure Research Laboratory, University of Science and Technology of China, Hefei, 230026, People’s Republic of China (Received 23 March 1999; accepted 1 July 1999)
A 100-nm CuFeS2 ultrafine powder was prepared through a solvothermal reaction at 200–250 °C. X-ray powder diffraction and transmission electron microscopy results revealed that chalcopyrite-phase CuFeS2 was crystallized with single-crystalline nature and preferential orientation growth. Mo¨ssbauer spectrum exhibited a six-peak hyperfine magnetic spectrum and a single nonmagnetic peak. Elemental analysis gave the atomic ratio of Cu:Fe:S of 1:1.02:2.10. The influence factors on the formation of CuFeS2 ultrafine powder are discussed.
I. INTRODUCTION
Chalcopyrite CuFeS2 has been known as an antiferrmagnetic semiconductor among the ternary semiconductors with chalcopyrite structure.1–3 It has novel optical and electrical and magnetic properties such as very small optical absorption edge (0.5–0.6 eV)4,5 and very high Ne´el temperature (550 °C),6,7 which has resulted in the potential applications as optoelectronic devices and magnetic materials. Traditionally, CuFeS2 powders were obtained from the direct combination of the elements or a sinter reaction of CuS and FeS,8,9 which required high temperature (600–800 °C) and long reaction time (2–3 days). The few methods available employed the homogeneous precipitation method, and the purity and physical form of precipitated product were not satisfactory.10 Although the literature on the synthesis of sulfides is extensive, to our knowledge, few of the published methods could be used to produce CuFeS2 ultrafine powder at milder conditions. Recently, various solution chemical synthesis techniques have been utilized to prepare some fascinating materials. This chemical method allows the particle size and their distribution and morphology to be well controlled.11–13 In this paper, we describe a solvothermal synthetic route to CuFeS2 ultrafine powder in the temperature range of 200–250 °C by using CuCl, iron powder, and sulfur as reactants. The synthetic reaction was carried out in an autoclave and associated with the following reaction: 3CuCl + 4Fe + 6S → 3CuFeS2 + FeCl3 .
a)
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J. Mater. Res., Vol. 14, No. 10, Oct 1999 Downloaded: 17 Dec 2014
In this process, the coordinating solvent such as ethylenediamine or pyridine plays an important role in the formation of CuFeS2. II. EXPERIMENTAL
An appropriate amount of analytical grade CuCl, Fe powder, and S were put into a titanium alloy autoclave of 50-ml capacity and then the autoclave was filled with ethylenediamine up to 85% of the total volume. The autoclave was kept at 200–250 °C for 8 h and then allowed to cool to room temperature naturally. The precipitate
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