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.
Description
Master
Keywords
Science , bandgap nanocrystalline , t-ZIRCONIA