Cathodoluminescence microscopy of superconducting and non-superconducting Tl2Ba2CuO6+δ polycrystals

Abstract

of superconducting and non-superconducting Tl2Ba2CuO6+x polycrystals. Physica C: Superconductivity and its Applications, Elsevier, 1996, 259, pp.121-130. <10.1016 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt età la diffusion de documents scientifiques de niveau recherche, publiés ou non, emanant desétablissements d'enseignement et de recherche français ouétrangers, des laboratoires publics ou privés.C. Diaz-Guerra, J. Piquera and C. Opagiste, Physica C 259 (1996) [121][122][123][124][125][126][127][128][129][130] AbstractLuminescence properties of Tl 2 Ba 2 CuO 6+x samples with different superconducting transition temperatures have been studied by cathodoluminescence (CL) in the scanning electron microscope. Independent of the crystal structure, tetragonal or orthorhombic, the CL spectra show two resolved bands at about 430 nm (2.9 eV) and 540 nm (2.3 eV), respectively. The results show that the 2.3 eV emission is related to oxygen content and is more intense in low-oxygen content superconducting samples. It is proposed that this band is related to a complex center involving oxygen vacancies. A comparison of spectra from Tl 2 Ba 2 CuO 6+x and from precursors used in the synthesis (CuO x , Tl 2 Ba 2 0 5 ) has been carried out.

Cathodoluminescence Microscopy and Secondary Electron Emission in Mechanically Polished and Electron Irradiated YBa2Cu3O7−x Ceramics

“…Spectra recorded from the luminescent, plastically deformed areas surrounding the indentations, showed a clear increase of the 2.4eV band relative to the 2.8eV emission. An enhancement of the green CL emission has also been observed in the spectra recorded from polished T12Ba2CuO6+6 ceramics [16].…”

Electron beam induced compositional and structural changes in

“…In a previous work [21] performed with the same set of samples used here, it was concluded that the CL intensity distribution is not due to impurity phases. This conclusion was obtained from characterization studies regarding kinds and amounts of impurity phases.…”

“…SEE and CL can provide complementary information on the defect structure in the oxygen sublattice of TBCO. The CL properties of TBCO have been previously discussed [14,21] and compared with similar results concerning other high-T c superconductors. On the other hand SEE results on TBCO samples have not been, to our knowledge, previously reported.…”

“…However, the reproducibility of results demonstrates the general trend, shown in the figure, of an increase of the SEE yield followed by a decrease at high T c . Since a higher T c value corresponds to a lower oxygen content [19][20][21][22], this result means that on decreasing oxygen content the SEE yield increases in a first stage and then decreases.…”

Structural and composition changes in superconducting ceramics locally irradiated by electrons

“…3). The 540 nm band, whose formation also involves a contribution from oxygen vacancies, 3,22 is very pronounced in the spectrum of the intermediate zone and is weaker in the spectrum of the peripheral zone. A reduction in oxygen content near the irradiated zone has also been observed by Raman scattering.…”