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Structure and Raman spectra of Nd x Y 1− x Ba 2 Cu 3 O 7−δ
Author(s) -
Hiep Duong Cong,
Lam Vu Dinh,
Hong Le Van
Publication year - 2001
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.768
Subject(s) - yttrium , raman spectroscopy , analytical chemistry (journal) , neodymium , ionic radius , chemistry , superconductivity , copper , raman scattering , crystallography , materials science , ion , oxide , condensed matter physics , laser , optics , physics , organic chemistry , chromatography
Nd x Y 1− x Ba 2 Cu 3 O 7−δ superconductor samples were prepared by the solid‐state reaction method. Yttrium was partially substituted by Nd with a content ranging from 0 to 100%. The phase purity of the given samples was checked by x‐ray diffraction, which showed that the samples are of the pure superconducting phase. The phase transition temperatures T c of all the samples were estimated from the temperature dependence of their resistance measured by the four‐probe technique. T c decreases slightly with increasing neodymium concentration substituted for yttrium. The Raman backscattering spectra were recorded at room temperature in the two polarization configurations z ( x ′ , x ′ ) − z and x ′ ( z , z ) − x ′ . The results show that the Raman shifts of the vibrational modes of the oxygen O4 and of the couple O2–O3 are affected by an internal pressure effect due to the substitution for yttrium by neodymium, which has a larger ion radius. Nd substitution also affects the crystalline structure and leads to disorder of the copper chain layers, which is the main reason for the appearance of Raman lines related to the vibration modes of Cu1 and O1 in the copper chain layer. Copyright © 2001 John Wiley & Sons, Ltd.