Synthesis and characterization of low bandgap nanocrystalline

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Date
2007
Authors
Prastomo, Niki
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Abstract
Nanocrystal t-ZrO2 powders were synthesized through a chemical route to seek a possibility if electronic doping would improve the electronics conductivity of the oxide. Y3+ was added as a stabilizer to retain tetragonal phase ZrO2 whereas Nb5+ was added for electronics doping. The phase formation and stabilization to achieve 100% pure t-ZrO2 were studied in detail encompassing all possible parameters which would contribute to the phase formation. Polymer decomposition and soft combustion methods were performed in this study to produce the doped zirconia. Precursor solutions were prepared from a mixture of zirconyl nitrate (ZrO(NO3)2), yttrium nitrate (Y(NO3)3), niobium tartarate (HNb(C4O6)) and TEA (triethanolamine) for polymer decomposition method, while zirconyl nitrate, yttrium nitrate, niobium nitrate (Nb(NO3)5) and glycine were used in soft combustion method. Several dopants compositions of zirconia powders were prepared by thermal decomposition method and were annealed at different temperatures. The synthesized powders were characterized using Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the powders calcined at 700ºC in this study ranges from 13.00 to 38.00 nm. The addition of Nb5+ did not alter the stability of the tetragonal phase formed in powder synthesis. Upon sintering different kind of atmosphere (argon-carbon, vacuum and air) it was found that at high sintering temperature, 1250°C to 1600°C, t-ZrO2 had transformed to m-ZrO2. However 100% t-ZrO2 was retained with sintering at 1400°C in vacuum condition. The optical band gap as measured by the UV-Visible Spectrometer for the sintered sample with t-ZrO2 gave a minimum value 4.00 eV, lower than the optical bandgap from commercial Yttria Stabilized Zirconia (YSZ) which was 6.09 eV.
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Master
Keywords
Science , bandgap nanocrystalline , t-ZIRCONIA
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