Preparation and phase control of nanocrystalline silver indium sulfides via a hydrothermal route
- PDF / 258,765 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 112 Downloads / 252 Views
A hydrothermal route was proposed to prepare and control nanocrystalline silver indium sulfides (orthorhombic AgInS2, tetragonal AgInS2, and cubic AgIn5S8). The reaction was carried out in an autoclave in the temperature range of 100–280 °C with AgCl, InCl3, and thiourea as reactants. X-ray powder diffraction patterns and transmission electron microscopy images showed that the products were AgInS2 and AgIn5S8 phases and well crystallized with grain diameter in the range of 20–70 nm. X-ray photoelectron spectra of the single AgIn5S8 phase revealed the surface stoichiometry (AgIn5.05S8.11), and its room temperature Raman spectrum showed a strong peak at 130 cm−1 and a weak peak at around 290 cm−1. The influence of reaction temperature on the phases in the final products was investigated. A possible reaction mechanism of the formation of silver indium sulfides was also briefly discussed. I. INTRODUCTION
The Ag–In–S system is currently of much interest because of the particular semiconductive properties of the ternary compound AgInS2. It is also a potential suitable material for opto-electronic devices due to its wide band gap in the visible region.1,2 The compound AgInS2 is generally considered to have the tetragonal chalcopyrite structure at low temperature and the orthorhombic structure at higher temperatures.3 Primary AgInS2 crystals with the chalcopyrite structure have been synthesized by normal freezing from the melt of stoichiometric mixtures.4 When a sample of chalcopyrite type AgInS2 was sealed in an evacuated glass tube and quenched around its melting point (880 ± 10 °C), the crystals AgIn5S8 with cubic spinel structure and AgInS2 with orthorhombic structure were obtained by Roth et al.5 These methods always involve high processing temperature, long reaction period, strict annealing processes, and special apparatus. The few routes available for preparation of the ternary chalcogenides of the Ag–In–S system employed the spray pyrolysis and homogeneous precipitation methods,6,7 and the purity and physical form and the stoichiometry of the final products were not satisfactory. During recent years, the chemical solution route has been emerging as one of many effective synthetic techniques for materials preparation.8,9 We have obtained a)
Address all correspondence to this author. Present address: Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong, SAR, China e-mail: [email protected] J. Mater. Res., Vol. 16, No. 12, Dec 2001
http://journals.cambridge.org
Downloaded: 09 Jun 2014
chalcopyrite structured AgInS2 and AgGaS2 from the solvothermal process.10 Hydrothermal route is one of the most promising chemical solution routes due to its economics and the high degree of compositional control.11–13 In this study, hydrothermal reaction was proposed to prepare and control nanocrystalline silver indium sulfides (orthorhombic AgInS2, tetragonal AgInS2, and cubic AgIn5S8). The reaction was carried o
Data Loading...
