The homogeneity region of neodymium- and lanthanum-substituted Bi2Sr2Cu2O8-based solid solutionsстатья
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Аннотация:This work concerns the determination of the homogeneity region for Bi2Sr2Ca1-xRxCu2O8+delta and Bi2Sr2-xCaRxCu2O8+delta (R = Nd, La) solid solutions. The phase composition of samples quenched from various temperatures was determined by semiquantitative X-ray powder diffraction analysis. In the case of lanthanides with similar or smaller ion radii substituting for alkaline-earth metals (the substitution of neodymium for calcium or of neodymium and/or lanthanum for strontium), the extents of the existence of Bi-2212 solid solutions are almost identical and approximate to x approximate to 0.8. This value is governed by the Cu+ ion fraction in crystal positions characteristic of Cu2+. In the case of La substituting for Ca, an appreciably narrower extent of the solid solutions was discovered, x approximate to 0.3, which is explained by a larger difference between the Ca2+ and La3+ ion radii.