Study of structural heterogeneity of HTSC Bi-ceramics

Using Bi-ceramics as an example, the authors estimate here the possibility of determination of the structural heterogeneity of HTSC materials from X-ray powder diffraction data. The heterogeneity is due to the presence of alternating layers of different types within individual microcrystals. Explicit information on alternating fragments of different height is provided by the intensity distribution data of basal reflections, therefore the authors studied X-ray diffraction patterns of oriented specimens. The diffraction patterns from unidimensionally disordered structures were simulated based on a previously devised procedure for the calculation of diffraction profiles of mixed-layer minerals. The comparison of calculated and experimental diffraction patterns testifies that defects in the samples are really caused by the presence of layers of different heights corresponding to the 2212 phase built into the matrix of the basic 2223 phase. The concentration of such defects reaches 20% with a high segregation degree of both layer types.