Mechanism and sintering kinetics of moistened Y—Ba—Cu—O powders

The influence of preliminary moistening of YBa2Cu3O7−x powder on the kinetics of sintering and recrystallization, and the evolution of element and phase compositions in the bulk and on grain boundaries, was studied by the methods of scanning electron microscopy, x-ray microprobe analysis, and x-ray diffractometry. It was established that moistening the powder leads to a change of the sintering mechanism from bulk diffusion (for unmoistened powder) to diffusion through solid layers in the grain boundary and subsurface regions of moistened powder, formed from the interaction products of YBa2Cu3O7−x with the moist atmosphere. The volume diffusion coefficients in YBa2Cu3O7−x, and the diffusion coefficients in the solid layers, were calculated from the sintering kinetics data. The diffusion coefficients in the solid layers were 2–3 orders of magnitude hither than the volume diffusion coefficients. This results in more rapid sintering of the moistened than the unmoistened powders.