OXIDE-ION CONDUCTIVITY IN SOME SUBSTITUTED RARE-EARTH PYROZIRCONATES

This paper reports oxide ion conductivity measurements on pyrozirconat es of neodymium and gadolinium in which the rare earth elements were p artially substituted by strontium, and zirconium partially substituted by aluminium. 5-10 atom% Sr and very little Al were found to enter th e pyrochlore lattice. ac impedance measurements have shown an enhancem ent of conductivity as a result of the incorporation of small amounts of Sr in both the pyrochlores. In the Gd2Zr2O7 system, this could be t raced to an improvement of the grain interior conductivity, by resolvi ng the grain interior and grain boundary contributions to the total co nductivity. Such a separation of the bulk and grain boundary conductiv ities could not be achieved in the Nd2Zr2O7-based compositions. The ob served variations in conductivity are explained in terms of the pyroch lore crystal chemistry.