  We report significant enhancement in superconducting properties of yttrium
substituted Ce1-xYxOFFeAs superconductors. The polycrystalline samples were
prepared by two step solid state reaction technique. X-ray diffraction
confirmed tetragonal ZrCuSiAs structure with decrease in both a and c lattice
parameters on increasing yttrium substitution (with fixed F content). With
smaller ion Y in place of Ce, the transition temperature increased by 6 K.
Yttrium doping also lead to higher critical fields as well as stronger inter
and intra-granular current density. The magnetization critical current density
increased by an order of magnitude at 30 K and 1 T magnetic field.
