Conductivity of gadolinium-doped sodium yttrium fluoride
Abstract Solids of different types have been used as solid electrolytes. NaYF 4 is such a solid now investigated from various points of view to yield valuable information about its transport properties. NaYF 4 type of solids have structure isomorphous with CaF 2 in which Cations are replaced randomly by Na and Y ions. In such a system, so far no studies are made to understand the dynamic behaviour of mobile fluoride ions and Yttrium ions at high temperatures. The conductivity of NaYF 4 pellets doped with different compositions of Gadolinium, x = 0.01, 0.03, 0.05, 0.10 and 0.15 was measured at several temperatures over the range of 20 to 500°C. It is found from these measurements that with increasing x, the conductivity increses and passes through a maximum at x = 0.05 at 300°C. The solid material is thermodynamically stable and can be prepared easily. These results are explained on the basis of thermal ionizations of impurity and imperfections.