ORIENTATION RELATIONSHIPS, MICROSTRUCTURE AND ELECTRICAL BEHAVIOUR OF GRAIN BOUNDARIES IN CERAMIC SUPERCONDUCTORS J.Y. LAVAL, C. DELAMARRE, M.H. BERGER et C. CABANEL J. Phys. Colloques, 51 C1 (1990) C1-991-C1-996 DOI: 10.1051/jphyscol:19901154