Cation Nonstoichiometry in Y123 Sintered Bulks and Thin Films

To clarify cation nonstoichiometry in Y123, Y123 sintered bulks and Y123 thin films starting from various yttrium compositions were synthesized. These samples were annealed under moderately high P_O2 to promote yttrium substitution for barium-site. Y123 sintered bulks showed decreases in T_c accompanying increases in a-axis length and decreases in c-axis length when they were synthesized from Y-excess composition or annealed at ~ 900°C under high P_O2 . Y123 thin films with various yttrium compositions showed different T_c behavior against oxygen annealing conditions, which might originate from the cation nonstoichiometry. These results suggest the existence of Y-excess composition even in Y123. Therefore, more attention must be paid for the cation nonstoichiometry in Y123 materials.