On the transport properties of K2ZnV2O7

Abstract

K₂ZnV₂O₇ has recently been reported as a promising oxide ion conductor. We have studied this material using a number of structure- and physical property-probing techniques. Our extensive characterisation using variable temperature synchrotron X-ray and neutron diffraction, impedance spectroscopy and tracer diffusion measurements of its transport properties, does not support the reports that K₂ZnV₂O₇ undergoes partial reduction at high temperatures, leading to the creation of vacancies and oxide ion conductivity. In particular, the lack of oxide ion diffusion observed by isotope exchange definitively rules out oxide ion conductivity within K₂ZnV₂O₇. Instead, we find that the high conductivity measured originates from the melting of a small amount of KVO₃ impurity in the sample, which is detectable by synchrotron X-ray and neutron diffraction.