QUANTITATIVE X-RAY PHASE-ANALYSIS AND EPR-SPECTRA IN THE SYSTEM Y2BACUO5-YBA2CU3O6+X

The quantitative phase analysis in the system Y2BaCuO5(2-1-1)-YBa2Cu3O 6+x(1-2-3) was performed by the X-ray powder diffraction (XRPD) method based on the comparison of the integral intensities of the X-ray diff ractions of the investigated system with the corresponding intensities of standard mixtures of (2-1-1) and (1-2-3) components of known compo sition. To avoid the orientation effects of the (1-2-3) components, th e selected mixtures were homogenized by the admixture of 50 mass% alph a-Al2O3. The constituent (2-1-1) showed no preferential orientation, n either in the bulk textured materials prepared by the quench and melt growth technique, nor in the samples ground to powder. The X-ray diffr action results were in accordance with the semiquantitative estimation of the concentration of the paramagnetic (2-1-1) phase obtained from the results of EPR measurements on powdered samples. On the other hand , the intensity of the EPR spectra strongly decreased in bulk material s due to the skin effect. The electric conductivity of (1-2-3) at room temperature causes the microwave fields to penetrate to a depth of ap proximately 10 mu m, which is the only EPR active region. (C) 1995 Aca demic Press, Inc.