Paper Type |
Contributed Paper |
Title |
Synthesis of Strontium-Doped ZnO-Based Nanopowders by Chemical Co-precipitation |
Author |
Niti Yongvanich*[a,b] |
Email |
niti.yongvanich@gmail.com |
Abstract: The effect of strontium doping on the microstructure of ZnO-based varistors was investigated. The starting multi-component nanopowders were synthesized by chemical co-precipitation. The studied samples are based on this general composition: Zn0.96Bi0.02(Co0.02-xSrx)Oβ with x = 0, 0.005, 0.01, and 0.02. The precipitates were characterized by Thermogravimetric Analysis (TGA), Transmission Electron Microscope (TEM) and X-ray Diffraction (XRD). TGA showed complete thermal decomposition after 590°C; hence, the calcination temperature was chosen to be 600°C. The morphology of the fired powders showed equiaxed in shape with some rod-like particles. There existed a wide range of particle size (70 – 300 nm). XRD revealed a Zincite structure (JCPDS database, 75-0576). No impurity peaks were observed under the XRD’s detection limit. Reduction in crystallite size upon increasing the amount of strontium was confirmed by peak broadening. By using the Sherrer’s formula, the averaged crystallite sizes decreased from 140.28 nm (x = 0) to 86.7 nm (x = 0.02) along [100]. A similar decreasing trend was also observed along the [002] direction. No significant difference in density for all compositions at all sintering temperatures. The densities rapidly increased to 5.40 g/cm3 (1,000°C) and remained constant afterwards. The sintered samples were multi-phasic as observed by XRD. Scanning Electron Microscope (SEM) demonstrated a decreasing trend in grain size in the samples sintered at 1000°C (from 2.82 μm in the x = 0 sample to 1.18 μm in the x = 0.02 sample). Results on the I-V behavior showed, upon increasing amount of strontium, a two-fold increase in breakdown voltage at the threshold current density of 1 mA/cm2 (up to 2,300 V/cm at x = 0.02). Such improvement is believed to be correlated to large grain boundary volumes associated with the varistor behavior. |
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Start & End Page |
1046 - 1054 |
Received Date |
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Revised Date |
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Accepted Date |
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Volume |
Vol.40 No.6 SPECIAL ISSUE 2 |
DOI |
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Citation |
Yongvanich N., Synthesis of Strontium-Doped ZnO-Based Nanopowders by Chemical Co-precipitation, Chiang Mai J. Sci., 2013; 40(6): 1046-1054. |
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