Oxygen Diffusivity and Defect Transport in Pure and Yb Doped Nano-crystalline Ceria

摘要

Oxygen (~(18)O) diffusivity in sol-gel synthesized nano-crystalline ceria films of average grain size of 3 nm and 7 nm, annealed at 300℃ and 450℃ for one hour respectively is examined by nuclear reaction analysis (NRA). Diffusivity and electrical transport properties measured by a. c. impedance spectroscopy were compared with microcrystalline ceria film of average grain size 38 nm annealed at 900℃ for one hour. Effect of enhanced oxygen diffusion along with reduced ionic transport in nano-crystalline ceria and reduced oxygen diffusion along with enhanced ionic transport in microcrystalline ceria are correlated to long range ordering, grain boundary scattering and defect density. Enhancement in the conductivity with reduction in activation energy from 1 eV to 0.5 eV in the case 4 atom% ytterbium (Yb) doped ceria compared to pure ceria is a result of increased oxygen vacancies taking part in the defect transport.