Improvement of Electrical Conductivity of Trivalent Rare‐earth Cation‐doped Neodymium Zirconate by Co‐doping Gadolinium and Ytterbium

Abstract

AbstractPyrochlore oxides of A2Zr2O7, where A represents trivalent rare‐earth elements, have a high electrical conductivity, which makes them suitable for applications as high‐temperature solid electrolytes. The influence of Gd and Yb cations co‐doping at the Nd site on structure and electrical conductivity of a pyrochlore oxide Nd2Zr2O7 is investigated using X‐ray diffraction and impedance spectra measurements. Different zirconate ceramics of Nd2Zr2O7, Nd1.8Gd0.2Zr2O7, Nd1.8Gd0.1Yb0.1Zr2O7, Nd1.4Gd0.6Zr2O7 and Nd1.4Gd0.3Yb0.3Zr2O7 are prepared by pressureless‐sintering method at 1,973 K for 10 h in air. Nd2Zr2O7 doped with Gd and Yb cations at the Nd site exhibit a single phase of pyrochlore‐type structure. The measured values of the total conductivity obey the Arrhenius relation. Nd2Zr2O7 and its doped zirconate ceramics are oxide‐ion conductors in the oxygen partial pressure range of 1.0 × 10–4 to 1.0 atm at all test temperature levels. The total conductivity increases with reducing average ionic radii of A‐site rare‐earth cations. The dual Yb+Gd intermix doping causes a distinctly enhanced total conductivity as compared to unmodified Nd2Zr2O7 and singly Gd‐doped zirconate ceramics. The highest total conductivity value obtained in this work is 1.02 × 10–2 S cm × 1 at 1,173 K for Nd1.4Gd0.3Yb0.3Zr2O7 ceramic.