MECHANISM AND SINTERING KINETICS OF MOISTENED Y-BA-CU-O POWDERS

The influence of preliminary moistening of YBa2Cu3O7-x powder on the k inetics of sintering and recrystallization, and the evolution of eleme nt and phase compositions in the bulk and on grain boundaries, was stu died 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 dif fusion (for unmoistened powder) to diffusion through solid layers in t he grain boundary and subsurface regions of moistened powder, formed f rom the interaction products of YBa2Cu3O7-x With the moist atmosphere. The volume diffusion coefficients in YBa2Cu3O7-x, and the diffusion c oefficients in the solid layers, were calculated from the sintering ki netics data. The diffusion coefficients in the solid layers were 2-3 o rders of magnitude higher than the volume diffusion coefficients. This results in more rapid sintering of the moistened than the unmoistened powders.