氧化锌纳米线

Cryst. Res. Technol. 38, No. 6, 429 – 432 (2003) / DOI 10.1002/crat.200310053

© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 0232-1300/03/0606-0429 $ 17.50+.50/0

Asymmetric twinning crystals of Zinc oxide formed in a

hydrothermal process

HaiYan Xu, Hao Wang*, YongCai Zhang, Shu Wang, ManKang Zhu, Hui Yan

The Key Laboratory of Advanced Functional Materials of China Education Ministry, Beijing University of

Technology, Beijing 100022, China

Received November 14, 2002, revised 10 January 2003, accepted 18 February 2003

Published online 15 June 2003

Key words zinc oxide, hydrothermal method, asymmetric shape.

PACS 81.05.Je, 81.10.Dn

Well crystallized ZnO powders with various morphologies such as hour glass-shaped, shortened prismatic,

flake-like and prismatic form have been synthesized by adopting the system of Zn(Ac)2-KOH-H 2O via a hydrothermal process at 200°C for 2 h. It was found that the as-synthesized hour glass-shaped ZnO

crystallites are asymmetric both in shape and stoichiometry: while the atomic ratio of O/(Zn+O) at the bigger

end ranges from about 60% to 40% along the polar axis of the hour glass-shaped ZnO crystallites, the atomic

ratio of O/(Zn+O) at the smaller end remains almost constant at approximately 50%.

1 Introduction

Zinc oxide (ZnO), as a wide band gap (3.37 eV) semiconductor with a large exciton binding energy (60 eV), has been extensively investigated due to its promising applications in short-wavelength light-emitting, transparent conductor, piezoelectric materials and room temperature ultraviolet lasing [1]. So far, several preparation procedures including sol-gel method [2], evaporative decomposition of solution [3], wet chemical synthesis [4], gas-phase reaction [5] and hydrothermal synthesis [6, 7], etc. have been developed to obtain ZnO crystallites. A variety of morphologies such as prismatic forms [8], ellipsoidal [9], bi-pyramidal and dumbbell-like [10], nanorods [11], nanowires [12] and spheres [13] have been synthesized during the last decade, and the growth mechanisms of ZnO crystallites with different shapes have also been discussed.

In this study, well crystallized ZnO powders with various morphologies such as twinning hour glass-shaped, shortened prismatic, flake-like and prismatic form were synthesized by adopting the system of Zn(Ac)2-KOH-H 2O via a hydrothermal process. We found an interesting phenomenon in the as-synthesized hour glass-shaped ZnO crystallites: the two part are asymmetric both in shape and stoichiometry: the atomic ratio of O/ (Zn+O) at the bigger end ranges from about 60% to 40% along the polar axis of the hour glass-shaped ZnO crystallites, while the atomic ratio of O/ (Zn+O) at the smaller end remains almost unchanged at approximately 50%.

2 Experimental Section

In a typical process, mixed aqueous solution of 6.5 ml Zn(CH 3COO)2 (1 mol/l) and 26 ml KOH (0.25-2.00 mol/l) was transferred into a 50 ml Teflon-lined autoclave and heated at 200 o C for 2 hours. The as-formed white precipitate was collected and washed several times with deionized water, then dried at 80 o C.

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* Corresponding author: e-mail: haowang@