Influence of oxygen deficiency and Nd/Ba substitution on critical currentsin Nd1+xBa2-xCu3Oy single crystals

Single crystals of the solid solution Nd1+xBa2-xCu3Oy have been grown from BaO-CuO flux in ZrO2/Y crucibles. Various Nd contents could be achieved by growing in different oxygen partial pressures or by subsequent thermal trea tments, which led to a spinodal decomposition. To suppress the influence of oxygen defects, first all crystals have been high-pressure oxidized severa l times. In a second series, the oxygen content of stoichiometric crystals have been reduced step by step by annealing in 1 bar oxygen at different te mperatures. The peak effect of the critical current and the irreversibility field are studied as a function of oxygen content, Nd/Ba ratio, and Nd/Y s ubstitution of the crystals. The influence of these different defects and t heir combination on the optimization of the critical current density is dis cussed.