SYNTHESIS AND INVESTIGATION OF SR-CONTAINING 223 AND 1222 COMPLEX OXIDES IN THE R-SR-CE-CU-O SYSTEM (R = PR, ND, SM-GD, DY-YB AND Y)статья
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Дата последнего поиска статьи во внешних источниках: 9 ноября 2013 г.
Аннотация:An extended family of layered complex copper oxides has been synthesized in the system R2O3-SrO-CeO2-CuO (R=Pr, Nd, Sm-Gd, Dy-Yb and Y). The compounds were studied by X-ray powder diffraction, electron microscopy and EDS analysis. Eu1.6Sr1.8Ce0.6Cu3O8.6 (a=3.8439(2) angstrom, c=28.09(1) angstrom) and Y1.5Sr1.8Ce1.0Cu2.7O8.6 (a=3.8160(7) angstrom, c=29.120(5) angstrom), belonging to two structural groups of 223- and 1222-type, respectively, were chosen for Rietveld structure refinement. Their structures can be described as 14-layered stackings along the c-axis. The compounds with larger lanthanides (R=Pr-Gd) are isostructural with Ba-containing 223 phases, e.g. (R, Ba)2(R, Ce)2Cu3O8+delta. Among the synthesized compounds only the ones with R=Sm and Eu have been shown to be superconductors (T(c)=30 and 36 K, respectively) after high-pressure oxygen treatment (120 atm). 1222 phases with smaller rare earth elements (R=Dy-Yb and Y) differ from 223 phases in composition and lattice parameters, having structures which are more similar to (Pb, Cu)-1222, e.g. (Pb, Cu) (Eu, Ce)2(Sr, Eu)2Cu2O8+delta. Compounds of 1222-type did not become superconducting even when treated with high-pressure oxygen.