Mass transfer and phase formation processes accompanying interdiffusio
n in the Dy2O3-BaO-CuO system are studied at 930 degrees C in air. Sev
eral phases formed by reaction diffusion are identified, and their cat
ion stoichiometry ranges determined. Mass transfer in this system occu
rs primarily through diffusion of Cu and Ba cations via vacancies of s
ingle-crystal DY2O3. Structural and superconducting properties of a bu
lk DyBa2Cu3O7+delta single crystal are studied.