Defective structures, surface textures, oxygen mobility, oxygen storage capacity (OSC), and redox properties of RE0.6Zr0.4O2 and of RE0.6Zr0.4-xYxO2 (RE = Ce, Pr; x = 0, 0.05) solid solutions have been investigated using X-ray diffraction (XRD), temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), O-2-H-2 and O-2-CO titration, O-18/O-16 isotope exchange, CO pulsing reaction, and X-ray photoelectron spectroscopy (XPS) techniques. The effects of doping noble metal onto RE0.6Zr0.4-xYxO2 on oxygen mobility and surface oxygen activities have also been studied. Based on the experimental outcomes, we conclude that: (i) a Pr-based solid solution has better redox behavior than a Ce-based one; (ii) incorporation of yttrium ions in the lattices of CZ and PZ solid solutions could result in an enhancement in oxygen vacancy concentration, Ce4+/Ce3+ and Pr4+/Pr3+ redox properties, lattice oxygen mobility, and oxygen storage capacity; and (iii) doping the noble metal (Rh, Pt, and Pd) onto RE-based solid solution has positive effect on the properties concerned in this work. (C) 2004 Elsevier B.V. All rights reserved.