Low angle grain boundary transport properties of undoped and doped Y123 thin film bicrystals

Undoped and Ca- or Ag-doped YBa2Cu3Ox (Y123) thin films were prepared by pu lsed laser deposition on symmetric low angle SrTiO3 bicrystals (4, 8, 12, 1 6 degree misorientation angle). The electrical transport properties of the inter- and intragrain critical current densities and V-I curves were invest igated at 77K in magnetic fields up to 6T. Ca-doped Y123 bicrystal films (1 0 % Ca substitution) showed no significant j(c)-enhancement at 77K in zero field but a strongly decreased j(c) at higher magnetic fields due to a redu ced irreversibility field at 77K. Ag-doped Y123 bicrystal films showed incr eased critical current densities at higher fields and a slightly shifted tr ansition from strong to weak link behavior compared to undoped Y123 bicryst al films.