Enhanced sinterability and electrical properties of GdSmZr ₂O₇ by addition of nickel oxide

The effect of nickel oxide addition on the sintering behavior and electrical properties of the GdSmZr₂O₇ ceramic has been investigated. The crystal structure, microstructure and electrical properties of the GdSmZr₂O₇ ceramic incorporated with or without 1 wt.% nickel oxide are characterized by the X-ray diffraction, field-emission scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The GdSmZr₂O₇ ceramic exhibits a single phase of the pyrochlore-type structure. No chemical reaction between GdSmZr ₂O₇ and NiO is found in the sintered samples. The grain, grain boundary, and total conductivity of the GdSmZr₂O₇ ceramic with or without NiO addition obey the Arrhenius relation. The addition of a small amount of NiO to the GdSmZr₂O₇ ceramic greatly promotes the densification process, achieving 93% of the theoretical density after sintering at 1773 K in air. This reduces the sintering temperature by about 200 K, without adversely affecting the total conductivity of the GdSmZr₂O₇ ceramic. The GdSmZr₂O₇ ceramic with 1 wt.% NiO addition is an oxide-ion conductor in the oxygen partial pressure range of 1.0 × 10^-4 to 1.0 atm at all test temperature levels.