Most studies of solids at high temperatures have concentrated on rare gases or metals. However, in the last few years, the special properties of ionic solids at high temperatures have become increasingly important, with applications to geophysics, ceramic processing, nuclear fuels, solid-state electrolytes, and so on. This volume includes a review by W Hayes and M Hutchings on some of the recent experiments, notably comprehensive work on crystals with fluorite structure, including uranium dioxide. Such experiments can be both difficult to perform and are equally difficult to interpret. There...