Iron-containing superconductors from the viewpoint of chemists: thermodynamic stability and substitution limits in La1–xLnxFeAsO1−y hightemperature superconductors (Ln = Ce–Er and Y).

Abstract

Within the framework of V. S. Urusov’s crystal energy approach, we calculated mixing energies (interaction parameters), critical decomposition (stability) temperatures and built the domes of the decomposition of solid solutions of the following systems: La_1−xCe_xFeAsO_0.65, La_1−xPr_xFeAsO_0.65, La_1−xNd_xFeAsO_0.65, La_1−xPm_xFeAsO_0.65, La_1−xSm_xFeAsO_0.65, La_1−xEu_xFeAsO_0.65, La_1−xGd_xFeAsO_0.65, La_1−xTb_xFeAsO_0.65, La_1−xDy_xFeAsO_0.65, La_1−xHo_xFeAsO_0.80, La_1−xEr_xFeAsO_0.75, La_1−xY_xFeAsO_0.80, La_1−xY_xFeAsO_0.60, La_1−xSm_xFeAsO_0.85, whose components are isostructural with ZrCuSiAs. It is shown that the magnitude of the mixing energy is determined mainly by the difference in sizes of the substituting structural units.