Abstract: The invention provides a method of manufacturing a doped i X—Ba—Cu-0 material, the method comprising the steps of: a) mixing an X—Ba-L-0 or X—Ba—Cu-L-0 material with an X-1 Ba—Cu—O material; and b) crystallising the mixture; 1 wherein each X is independently selected from a rare earth (Group IIIB) element, yttrium, a combination of rare earth elements, or a combination of yttrium and a rare earth element; and L is selected from U, Nb, Ta, Mo, W, Zr, Hf, Ag, Pt, Ru and Sn. The invention further provides a doped material manufactured by the method of the invention.