New Phases of YBaCuGeO Superconductors Identified from X-ray Diffraction and Infra-red Absorption Measurements

Authors : Ahmed ABOARAIS, Mohamad Ahmad Taher DAWOUD

Pages : 33-41

Doi:10.3906/sag-1202-53

View : 13 | Download : 9

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :X-ray powder diffraction patterns and infra-red absorption spectra have been evaluated and analysed for the Y1 Ba2 Cu3 O7-d - Gex compound samples prepared by the solid state reaction with x values ranging from 0.0 to 1.13. All samples show bulk superconductivity above liquid nitrogen temperature using the levitation test insert ignore into journalissuearticles values(Meissner effect);. Samples with Ge content up to x = 0.2 have offset Tc between 83K and 92K while the sample with x = 1.13 shows semiconducting behavior above 100K. As a result of the solid state interaction between YBCO and Ge, new phases are observed and determined, mainly three phases are concluded from X-ray powder diffraction analysis: insert ignore into journalissuearticles values(i); Ba2GeO4 insert ignore into journalissuearticles values(ii); Y2BaCuO5 insert ignore into journalissuearticles values(iii); BaCO3. The unit cell parameters a, b and c of the orthorhombic superconducting phase are calculated for all the prepared samples. The anisotropy factor is evaluated and related to the new structural phases in YBCO-Ge composite system. The I-R absorption spectra for the samples with orthorhombic symmetry have been determined. The phonon modes between ~ 400 cm-1 and 630 cm-1 are attributed to the Cu - O octahedron and pyramid vibrations for the CuO2 -planes and CuO-chains, while the peaks in the range from ~ 700 cm-1 to ~ 860 cm-1 may be due to defects such as the new phase Ba2GeO4 and the green phase Y2BaCuO5. The obtained results are discussed according to the superconductor - semi-conductor composite model and with the phonon-mediated charge transfer between CuO2 -planes and CuO- chains through apex oxygen insert ignore into journalissuearticles values(BaO);.
Keywords : Superconductors, X ray, Infra red, YBCO, Ge