Single crystals represent perfection in Physics, and we grow large, high quality crystals using the optical floating zone furnace at Royal Holloway. Dr S. Uthayakumar has successfully grown high quality single crystals of the first cm3 sized crystals of a range of cathode materials for lithium-ion and sodium-ion batteries. He has also grown powder and single-crystal samples of thermoelectric materials, enabling physical property measurements, neutron and synchrotron x-ray experiments. For example, small high quality single crystals for thermal conductivity and inelastic x-ray scattering experiments, and large crystals for inelastic neutron scattering experiments, have explained the suppression of thermal conductivity in so-called “rattler” thermoelectrics, see Fig.1.
Fig. 1. (a) Supercell of sodium cobaltate showing rattling mode. (b) Phonon dispersion measured using inelastic x-ray scattering (red symbols) and calculated using DFT (colour contour diagram). (c) Thermal conductivity (black symbols) compared with calculations. [D.J. Voneshen et al. Nature Materials 12, 1028-1032 (2013).]
