PhD in Physics

Supervisors: Prof. Anthony Powell and Dr Paz Vaqueiro/nProject Overview:/nA four-year PhD studentship, fully funded by AWE, is available for a research project to develop novel low-thermal conductivity materials, through the preparation of high-entropy oxides, with applications in solid-state thermal batteries. These are batteries in which the electrolyte, a solid under stored conditions, melts on application of a thermal pulse, leading to charge flow and normal battery operation./nHigh-entropy materials contain five or more atoms/cations distributed over a single crystallographic site. The resulting configurational entropy contributes a stabilising term to the free energy, enabling the formation of otherwise energetically unfavourable materials. This entropic stabilisation can force cations into non-preferred coordination geometries, leading to significant local lattice distortion and disorder in interatomic force constants. These effects impede the propagation of heat-carrying phonons, resulting in exceptionally low thermal conductivity./nThe initial focus of the project will be on materials of general formula A2B2O6 and A2B2O7 that adopt the defect pyrochlore and pyrochlore structures respectively. The project will seek to introduce multiple cations at the A site, primarily comprising closed-shell and lone-pair-containing species, to enhance disorder and lattice strain. The project will then extend to oxides with alternative cage-like structures./nThe project will involve a range of solid-state synthesis techniques, powder X-ray diffraction and electron microscopy together with measurement of thermal, spectroscopic and transport properties. Detailed structural studies will utilise powder neutron diffraction, augmented by pair distribution function (PDF) analysis to probe changes in the local structure./nThis project provides a comprehensive training in advanced materials synthesis and characterisation techniques and offers the opportunity to work on a scientifically challenging problem at the interface of materials chemistry and condensed matter physics, with relevance to thermal management technologies./nLocation: Reading