Elsevier

Materials Research Bulletin

Volume 45, Issue 11, November 2010, Pages 1703-1706
Materials Research Bulletin

In2O3 microcrystals obtained from rapid calcination in domestic microwave oven

https://doi.org/10.1016/j.materresbull.2010.06.056Get rights and content

Abstract

The simple way to prepare In2O3 microcrystals is reported in this paper. The precursor, In(OH)3 microstructures, were obtained using the Microwave-Assisted Hydrothermal (MAH) Method. By annealing as-prepared In(OH)3 precursor at 500 °C for 5 min in a domestic microwave oven (MO), In2O3 microcrystals were prepared, inheriting the morphology of their precursor while still slightly distorted and collapsed due to the In(OH)3 dehydration process which was studied by thermal analysis. The In(OH)3 and In2O3 were characterized using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. These techniques confirm the chemical dehydration of In(OH)3 and the formation of In2O3 powders. The domestic MO promotes a rapid structural organization as compared with a CF (conventional furnace). The MAH method and the subsequent annealing in a domestic MO were shown to be a low cost route for the production of In2O3, with the advantages of lower temperature and smaller time.

Introduction

The synthesis of different dimensional nanostructures is of great importance in the study of physical properties of nanomaterials in the construction of functional nanodevices. Indium oxide (In2O3), an n-type semiconductor with a wide band gap of about 3.6 eV, has been widely used as a solar cell, a window heater, materials for a flat-panel display and gas sensors [1], [2]. Nanostructures of this oxide (nanobelts [3], [4], nanowires [5], [6], nanofibers [7], [8], octahedrons [9], nanocubes [5], [10], nanotubes [11], [12], and nanoparticles [13], [14], [15]) have been synthesized by different synthesis methods such as thermal evaporation of In2O3 [3], chemical vapor deposition [4], and wet chemical methods [16], [17], [18], [19].

In2O3 materials have been obtained by heating their In(OH)3 or InOOH precursors with the desired morphology using conventional hydrothermal and conventional furnace [13], [20], [21], [22], [23]. However, to produce In2O3 single crystals using these syntheses method, elevated calcination temperature and reaction time were required.

Recently, the domestic microwave oven (MO) has been successfully employed to obtain materials [24], [25]. Advantages such as rapid heating, selective material coupling and enhanced reaction kinetics make the microwave process an attractive route for materials synthesis [26], [27].

In this paper, In2O3 nanocubes were quickly synthesized after annealing a In(OH)3 precursor at 500 °C for 5 min in a domestic MO. This process is simple and clean, does not require long annealing times and is more economical than conventional methods. The crystalline structure, morphology and particles size of the as-prepared In(OH)3 precursor and In2O3 were investigated using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy.

Section snippets

Experimental

The experimental procedure is as follows: 3.6 mmol indium (III) chloride (99% purity, Aldrich) was dissolved in 80 mL of deionized water under constant stirring for 30 min. The mixture was then transferred into a Teflon autoclave which was sealed, and the reaction system was heated under hydrothermal conditions of temperature at 140 °C for 60 min (heating rate fixed at 25 °C/min) using microwave irradiation (2.45 GHz, maximum power of 800 W). The pressure into the autoclave was stabilized at 3.0 atm.

Results and discussion

The conversion process of the as-prepared In(OH)3 cubic and rectangular-shaped microstructures during a calcination by MO in air was studied by thermogravimetry and differential thermal analysis, Fig. 1. An analysis of the In(OH)3 TGA curve showed an abrupt weight loss occurring mainly in the temperature range from 180 to 600 °C, and a weight loss of about 17% attributed to chemical dehydration (see Eq. (1)). Above 600 °C, no obvious weight loss was observed. The DTA curve showed an endothermic

Conclusions

The In(OH)3 precursor was formed using the MAH method at 140 °C for 60 min. In2O3 cubic microstructures have been successfully synthesized from indium particles by thermal decomposition of In(OH)3 precursor at 500 °C for 5 min using microwave radiation. In2O3 microcrystals present a morphology of their precursor which is slightly distorted and collapsed due to the dehydration process of the In(OH)3 precursor. The MAH method and the subsequent annealing in a domestic MO were shown to be a low cost

Acknowledgements

The authors thank the financial support of the Brazilian research financing institutions: FAPESP-CEPID 98/14324-8, CNPq and CAPES.

References (35)

  • T. Takada et al.

    Sens. Actuators B

    (1993)
  • J.S. Jeong et al.

    Chem. Phys. Lett.

    (2004)
  • H.Q. Yang et al.

    Mater. Res. Bull.

    (2009)
  • Y.B. Li et al.

    Adv. Mater.

    (2003)
  • X.Q. Wang et al.

    Sens. Actuators B

    (2009)
  • Y.-M. Zhou et al.

    Mater. Res. Bull.

    (2008)
  • Z. Zhan et al.

    Mater. Res. Bull.

    (2007)
  • C.S. Riccardi et al.

    Solid State Ionics

    (2009)
  • D.P. Volanti et al.

    J. Alloy Compd.

    (2008)
  • D. Keyson et al.

    J. Mater. Process. Technol.

    (2007)
  • A.Z. Simoes et al.

    Mater. Charact.

    (2008)
  • L.S. Cavalcante et al.

    Chem. Eng. J.

    (2008)
  • W.B. White et al.

    Spectrochim. Acta A

    (1972)
  • G. Korotcenkov et al.

    Thin Solid Films

    (2005)
  • I. Hamberg et al.

    J. Appl. Phys.

    (1986)
  • Z.W. Pan et al.

    Science

    (2001)
  • X.X. Xu et al.

    Inorg. Chem.

    (2009)
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