2011 Postgraduate Research Competition - UNSW Science - The ...

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WO3 Nanostructured Thin Film Prepared by
Cathodic Electrodeposition and its
Photoelectrochemical Properties
Wai Ling Kwong and Charles C Sorrell
School of Materials Science & Engineering
Abstract
Nanostructured tungsten trioxide (WO3) has shown great promise as photoelectrode
material for the application in photoelectrochemical water splitting due to its remarkable
stability in acidic aqueous environment, good electrical conductivity, non-toxicity and a
small band gap of 2.6-3.0 eV, leading to the adsorption of a reasonable fraction of the
electromagnetic spectrum. The large specific surface area which provides more active
reaction sites and the absence of the conventional space-charge layer which resulted in
different charge separation in a nanocrystalline WO3 play important role in surpassing its
counter part (planar film) in photoelectrochemical performance. In this study,
nanostructured WO3 thin films were synthesized by cathodic electrodeposition technique
because it offers a cost-effective way to deposit adhesive large-area stoichiometric thin films
on electro-conductive substrates at low-temperature without the need of expensive
instrument. The films were potentiostatically deposited from peroxotungstic acid aqueous
solutions and its photoelectrochemical properties were studied. Uniform WO3 nanostructured
thin films were obtained and they demonstrated high crystallinity and optical adsorption
upon annealing. The optical, structural and photoelectrochemical properties of
nanostructured WO3 were found to be tailored by varying the concentration of tungsten,
electrolyte pH, deposition potential, temperature and post-annealing.
Electric field-induced transformations in the
lead-free piezoceramic 94%(Bi1/2Na1/2)TiO3-6%BaTiO3
Abstract
Hugh Simons and Mark Hoffman
School of Materials Science & Engineering
The structural origin of the large electric-field-induced strain in bulk 94%(Bi1/2Na1/2)TiO3-
6%BaTiO3 has been investigated using in-situ neutron diffraction. This material is of particular
interest as a substitute for lead zirconate titanate in high strain actuator applications. The
unpoled structure shows an unusual combination of near-cubic phases with differing tilting
modes of the oxygen octahedra and a periodic modulation of the atomic positions. An
electric field was applied stepwise to a maximum of 4kV/mm with texture patterns collected
at each field value. It was found that low-magnitute electric fields (