Building hexagonal perovskites based on large B-site cations for advanced materials applications
Summary
The student will use synthetic materials chemistry, physical property measurements, synchrotron X-ray and neutron scattering to develop and characterise new hexagonal perovskites for applications including superionic conduction, nuclear waste storage and complex magnetism.
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Synopsis
Hexagonal perovskites containing large cations such as Ba(II) in the 12-fold coordinate A-sites have long been of interest for their extreme structural and compositional flexibility. This project is concerned with such materials where large cations are also resent in the octahedral B-sites, increasing the flexibility even further. Recent results in Dr Ling’s group have shown that these materials exhibit far more interesting and complex structural behaviour than previously realised. Compounds such as Ba(4)Sb(2)O(9), Ba(3)SrSb(2)O(9) and Ba(4)Ta(2)O(9) were reported in the 1960’s, but their structures were insoluble with the techniques available at the time, and they have been almost completely ignored since then. The group recently revisited these compounds and solved their structures using modern techniques including high-resolution neutron powder diffraction, synchrotron X-ray diffraction and ab initio geometry optimisation calculations. At room temperature they appear to be thermodynamically unstable but kinetically robust, giving them potential as radioactive actinide storage matrices; while at high temperature they undergo a series of displacive and reconstructive phase transitions, giving them potential as superionic conductors. Finally, their layered hexagonal structures suggest interesting magnetic properties if some of the B-site cations could be replaced by magnetic ones.
A PhD position is now open for a motivated and talented student to pursue these possibilities by developing this promising family of materials. The project will involve materials chemical synthesis, crystallography (including neutron and synchrotron X-ray scattering) and physical property characterisation. Particular emphasis will be placed on the growth of large (cm-scale) single crystals and on the use those crystals for detailed physical property characterisation and elastic/inelastic neutron scattering experiments at the OPAL research reactor near Sydney and similar major facilities overseas.
Additional Information
Dr Ling’s laboratories at the School of Chemistry have a comprehensive set of facilities for materials synthesis and characterisation, including Australia's only infra-red floating zone image furnace for the synthesis of large (cm-scale) single crystals of high melting-point (up to 2200ºC) oxides, nitrides and intermetallics. In the School we have a new X-ray powder diffractometer (XRD) with excellent in situ (temperature and atmosphere) capabilities and a Physical Properties Measurement System (PPMS), both of which are dedicated to materials chemistry research.
Neutron scattering is a key tool in Dr Ling’s research. Neutrons are strongly scattered by light elements such as hydrogen and oxygen, which are difficult to observe using X-rays in the presence of heavy metals. Neutrons also possess spin (s = ½) and are scattered by unpaired electrons, so they can be used to study magnetic structures and the dynamics of electronic exchange that gives rise to them. This project will make extensive use of the new OPAL research reactor at Lucas Heights near Sydney, and (for certain specialised experiments) overseas neutron facilities such as ISIS in the UK and the ILL in France.
Scholarships are available to high quality students. Most local students in the laboratory are supported by an Australian or University Postgraduate Award and International students by other scholarships. Please contact me for further details.
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Opportunity ID
The opportunity ID for this research opportunity is: 575