Electrical conductivity and oxygen diffusivity in Cu- and Ga-doped Pr2NiO4

Oxygen diffusivity in Cu- and Ga-doped Pr2NiO4 + δ was investigated with tracer diffusion and secondary ion mass spectroscopy (SIMS) analysis in order to estimate the oxide ion conductivity. Doping Ni sites in Pr2NiO4 with Cu and Ga doubles the oxygen diffusivity, and the measured activation energy for diffusion is 0.64 ± 0.04 eV for Pr1.9Ni0.75Cu0.25O4 + δ and 0.57 ± 0.05 eV for Pr1.9(Ni0.75Cu0.25)0.95Ga0.05O4 + δ. This result suggests that the diffusion mechanism was not changed by doping with Cu and/or Ga but diffusivity and amount of interstitial oxygen were changed. Hall-effect measurements suggest that holes are the main charge carriers in the Pr2NiO4 system. Furthermore, in this study, it was confirmed that Cu and Ga co-doping reduces both the hole concentration and mobility, even though the oxygen ion diffusivity is enhanced.