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.