synthesis, structure and properties of solid-state materials
My research approaches functional solid-state materials by focussing on structure as the key that relates their chemistry to their properties. These projects all involve synthesis, physical property measurements, crystallography and spectroscopy (especially neutron and synchrotron x-ray scattering). They also make use of ab initio (DFT) calculations and simulations to help understand structure and dynamics in the target materials, and to interpret experimental results.
Stabilising the fastest of fast-ion conductors with high valent transition metals
The high-temperature form of bismuth oxide, δ-Bi2O3, is among the best ionic conductors known, but is only stable above 750°C. It can be stabilised to room temperature by "doping" with transition metals such as Nb or Re, creating potential solid-oxide fuel cell membrane materials. However, the dopants also give rise to complex local ordering of oxide ions in their vicinity, degrading performance. This project seeks to understand how that ordering aff ects stability and conductivity, and use that understanding to develop new materials In particular, we will explore whether certain dopants (e.g. Mo6+) can be arranged to participate cooperatively in ionic transport, enhancing rather than degrading the conductivity.
Novel hydrated oxides for mixed ionic-electronic conduction
Mixed ionic-electronic conduction (MIEC) is a rare property required for fuelcell electrodes, as well as oxygen and humidity sensors. We recently discovered and characterised a new class of hydrated oxides Ba4M2O9.xH2O (M = Nb, Ta, Sb) that exhibit MIEC due to the presence of large voids and discrete hydroxide ions across three diff erent structural forms. The key breakthrough was to grow cm-scale single crystals in our fl oating-zone furnace (FZF) – a first for these materials – and use them for physical property and neutron scattering experiments. This project will use the FZF technique as the starting point to investigate the wide range of related barium oxides suspected of showing MIEC behaviour, but which have never been satisfactorily characterised.
Naturally layered multiferroics: combining properties on an atomic scale
Multiferroics exhibit both ferroelectricity (electrical polarisation, used in capacitors) and ferromagnetism (spin polarisation, used in transformers and data storage devices). They have important applications as sensors, actuators and – potentially – a new generation of data storage media. Unfortunately, because the two properties are usually mutually exclusive in a single material, all the multiferroics in current use are simply multilayer sandwiches of bulk ferroelectric and ferromagnetic materials. In this project we plan to resolve this incompatibility via an entirely new approach, in which we take naturally layered ferroelectric oxides and use them as "templates" into which we will substitute single atomic layers of magnetic cations.
For further information, please contact:
School of Chemistry
University of Sydney NSW 2006
Phone: +61 2 9351 4780