Chris Grovenor
Professor of Materials
+44 1865 273751
Chris Grovenor has interests in the application of advanced analytical techniques to understanding the relationship between chemistry and microstructure and the properties of a wide range of functional materials. Current areas of research include:
- Oxidation and hydriding mechanisms of Zr nuclear fuel cladding alloys (with Rolls Royce, Westinghouse, EPRI, EDF, CNL, Manchester University and Imperial College)
- Synthesis and characterisation of the new superconducting materials (with Prof. Susannah Speller). I am the Director of the £6.5M Centre for Applied Superconductivity funded by the Oxfordshire LEP and working with local companies and research organisations, and with the Clarendon Laboratory, on industrially relevant problems in applied superconductivity.
- I am the lead investigator of the NNUF management group overseeing the installation around the UK of £80m of new facilities for nuclear science and technology (www.nnuf.ox.ac.uk), including an access scheme for all UK researchers to use this state of the art equipment.
- Leadership of the group using high resolution SIMS analysis to study a variety of industrially relevant problems, including additives to improve the performance of perovskite solar cells, hydrogen (deuterium) pickup mechanisms in zirconium alloys and the mechanisms of degradation of solid state Li-on batteries.
- The application of thin film science for improving the performance of solid state batteries.
New Postgraduate Research Projects Available
Selected Publications
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Site-specific specimen preparation for SIMS analysis of radioactive samples.
November 2020|Journal article|J MicroscSecondary Ion Mass Spectrometry is an important technique for the study of the composition of a wide range of materials because of the exceptionally high sensitivity that allows the study of trace elements and the ability to distinguish isotopes that can be used as markers for reactions and transport processes. However, when studying nuclear materials, it is often necessary to analyse highly radioactive samples, and only rather few SIMS facilities are available in active environments. In this paper, we present a methodology using focussed ion beam milling to prepare samples from radioactive specimens that are sufficiently large to undertake SIMS mapping experiments over microstructurally significant regions, but with overall activities small enough to be readily transported and analysed by a SIMS instrument in a normal laboratory environment. Radioactive samples prepared using this methodology can also be used for correlative SIMS analysis with other analytical microscopies. SIMS results showing the distributions of deuterium in oxides on in-reactor corroded zirconium alloys are presented to demonstrate the potential of this sample preparation technique.focused ion beam (FIB), high-resolution secondary ion mass spectrometry (SIMS), hydrogen pickup, nuclear materials, sample preparation, zirconium alloys -
Fabrication of Li
1+x Alx Ge2-x (PO4 )3 thin films by sputtering for solid electrolytesOctober 2020|Journal article|Solid State Ionics© 2020 Elsevier B.V. Li1+xAlxGe2-x(PO4)3 (LAGP) thin films have been grown on sapphire substrates by RF magnetron sputtering and post annealing. The effects of varying sputtering parameters such as power and pressure were studied, and the deposited films were characterized to investigate how the ionic conductivity values depend on the microstructure. The composition of as-sputtered films was found to be more strongly influenced by power than the pressure. The films deposited at lower powers, which results in lower deposition rates, have compositions similar to that of the target. Heating the substrates during deposition is found to minimise the formation of pinhole defects in films subsequently annealed at higher temperatures. Post annealing leads to a gradual transformation from the as-sputtered amorphous phase to crystalline LAGP thin films. At high annealing temperatures (above 700 °C) both porosity and the GeO2 impurity phase appear in the films and result in lower ionic conductivities. We have optimised the processing conditions to achieve ionic conductivities in excess of 10−4 Scm−1 and activation energies as low as 0.31 eV in films only 1 μm thick, suggesting that LAGP could offer attractive properties as a thin film battery electrolyte material. -
In-situ TEM study of irradiation-induced damage mechanisms in monoclinic-ZrO
2 October 2020|Journal article|Acta Materialia© 2020 We have investigated the microstructural and crystallographic evolution of nanocrystalline zirconia under heavy ion irradiation using in-situ transmission electron microscopy (TEM) and have studied the atomic configurations of defect clusters using aberration-corrected scanning transmission electron microscopy (STEM). Under heavy ion irradiation the monoclinic-ZrO2 is observed to transform into cubic phase, stabilised by the strain induced by irradiation-induced defect clusters. We suggest that the monoclinic-to-cubic transformation is martensitic in nature with an orientation relationship identified to be (100)m∥(100)c and [001]m∥[001]c. By increasing the damage dose, both the formation of voids and irradiation-induced grain growth were observed. A model for the formation of voids is proposed, taking defect interactions into consideration. The study has also demonstrated that high resolution orientation mapping by transmission Kikuchi diffraction (TKD) combined with in-situ irradiation in a TEM is a powerful method to probe the mechanisms controlling irradiation-induced processes, including grain boundary migration, phase transformations and texture evolution. -
Characterisation of deuterium distributions in corroded zirconium alloys using high-resolution SIMS imaging
September 2020|Journal article|Acta MaterialiaHydrogen diffusion through the oxide grown on Zr alloys by aqueous corrosion processes plays a critical role in determining the rate of hydrogen pickup (HPU) which can result in embrittlement of fuel cladding and limit the burnup of the nuclear fuel it encapsulates. Mapping the hydrogen/deuterium distributions in these oxide layers, especially in the barrier layer close to the metal/oxide interface, is a powerful way to understand the mechanism of both oxidation and hydrogen pickup. Here we have characterised by high-resolution SIMS analysis the deuterium distribution in oxide layers on a series of Zr alloys, including autoclave-oxidised Zircaloy-4, Zr-1Nb and Zr-2.5Nb alloys, and in-flux and out-of-flux corroded Zr-2.5Nb samples. Pre-transition Zircaloy-4 samples show a high deuterium trapping ratio in the oxide and a higher diffusion coefficient than in oxides on the Nb-containing samples. Neutron irradiation increases the deuterium diffusion coefficient, the deuterium concentration in the oxide and the pickup fraction in Zr-2.5 Nb samples. Comparative NanoSIMS and EDX/SEM analysis demonstrates that the deuterium is not preferentially trapped at second phase particles in the oxides on any of the alloys studied, but there is direct evidence for trapping at the surfaces of small oxide cracks especially in Zircaloy-4 samples. The high resolution mapping of these hot-spots in 3D can provide unique information on the mechanisms of hydrogen uptake, and suggests that the development of interconnected porosity in the oxide may be the critical rate-determining mechanism that controls HPU in the aqueous corrosion of zirconium alloys in water-cooled reactors.FFR -
2020 roadmap on solid-state batteries
August 2020|Journal article|Journal of Physics: Energy -
A piperidinium salt stabilizes efficient metal-halide perovskite solar cells
July 2020|Journal article|Science -
A piperidinium salt stabilizes efficient metal-halide perovskite solar cells.
July 2020|Journal article|Science (New York, N.Y.)Longevity has been a long-standing concern for hybrid perovskite photovoltaics. We demonstrate high-resilience positive-intrinsic-negative perovskite solar cells by incorporating a piperidinium-based ionic compound into the formamidinium-cesium lead-trihalide perovskite absorber. With the bandgap tuned to be well suited for perovskite-on-silicon tandem cells, this piperidinium additive enhances the open-circuit voltage and cell efficiency. This additive also retards compositional segregation into impurity phases and pinhole formation in the perovskite absorber layer during aggressive aging. Under full-spectrum simulated sunlight in ambient atmosphere, our unencapsulated and encapsulated cells retain 80 and 95% of their peak and post-burn-in efficiencies for 1010 and 1200 hours at 60° and 85°C, respectively. Our analysis reveals detailed degradation routes that contribute to the failure of aged cells. -
NanoSIMS Imaging and Analysis in Materials Science.
June 2020|Journal article|Annual review of analytical chemistry (Palo Alto, Calif.)High-resolution SIMS analysis can be used to explore a wide range of problems in material science and engineering materials, especially when chemical imaging with good spatial resolution (50-100 nm) can be combined with efficient detection of light elements and precise separation of isotopes and isobaric species. Here, applications of the NanoSIMS instrument in the analysis of inorganic materials are reviewed, focusing on areas of current interest in the development of new materials and degradation mechanisms under service conditions. We have chosen examples illustrating NanoSIMS analysis of grain boundary segregation, chemical processes in cracking, and corrosion of nuclear components. An area where NanoSIMS analysis shows potential is in the localization of light elements, in particular, hydrogen and deuterium. Hydrogen embrittlement is a serious problem for industries where safety is critical, including aerospace, nuclear, and oil/gas, so it is imperative to know where in the microstructure hydrogen is located. By charging the metal with deuterium, to avoid uncertainty in the origin of the hydrogen, the microstructural features that can trap hydrogenic species, such as precipitates and grain and phase boundaries, can be determined by NanoSIMS analysis on a microstructurally relevant scale. -
Effect of the sintering temperature on the microstructure and superconducting properties of MgB2 bulks manufactured by the field assisted sintering technique
May 2020|Journal article|SUPERCONDUCTOR SCIENCE & TECHNOLOGYMgB2, field assisted sintering, processing temperature, microstructure, superconducting magnet, spark plasma sintering, connectivity -
Design and characterisation of ex situ bulk MgB2 superconductors containing a nanoscale dispersion of artificial pinning centres
March 2020|Journal article|SUPERCONDUCTOR SCIENCE & TECHNOLOGYMgB2, bulk, microstructure, processing