Browsing by Author "Zhou, Yusheng"

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Electricity generation based on vertically aligned PbZr0.2Ti0.8O3 nanowire arrays
(2012-05-01)
Chen, Cheng-Ying
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Liu, Te-Hsiang
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Zhou, Yusheng
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Zhang, Yan
;
Chueh, Yu-Lun
We statistically demonstrated the electricity generation from individual vertically-aligned/epitaxial PbZr0.2Ti0.8O3 (PZT) nanowires (NWs) using a conductive atomic force microscope (AFM). The measured outputs were analyzed in reference to the theoretically calculated piezopotential distribution in a bent NW. Our results show that the performance of the PZT NWs for electricity generation is at the same level as that of ZnO NWs although the piezocoefficient of PZT is high, due to high relative dielectric constant of PZT. Systematic investigating piezoelectricity from single PZT NWs will be useful for optimizing the performance for PZT nanogenerator applications. (C) 2012 Elsevier Ltd. All rights reserved.
In Situ Observation of Dehydration-Induced Phase Transformation from Na2Nb2O6-H2O to NaNbO3
(2012-10-25)
Jung, Jong Hoon
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Chen, Chih-Yen
;
Wu, Wen-Wei
;
Hong, Jung-Il
;
Yun, Byung Kil
We have monitored the phase transformation from a Sandia octahedral molecular sieve Na2Nb2O6-H2O to a piezoelectric NaNbO3 nanowire through in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements at high temperatures. After dehydration at 288 degrees C, the Na2Nb2O6-H2O becomes significantly destabilized and transforms into NaNbO3 with the increase of time. The phase transformation time is exponentially proportional to the inverse of temperature, for example, similar to 10(5) is at 300 degrees C and similar to 10(1) at 500 degrees C, and follows an Arrhenius equation with the activation energy of 2.0 eV. Real time TEM investigation directly reveals that the phase transformation occurs through a thermally excited atomic rearrangement due to the small difference of Gibbs free energy between two phases. This work may provide a clue of kinetic control for the development of high piezoelectric lead-free alkaline niobates and a deep insight for the crystallization of oxide nanostructures during a hydrothermal process.