The introduction of the Moessbauer nuclei 57Fe, 119Sn and 151Eu into Tl-based 12(n-1)n superconductors was investigated. The doped Tl-based superconductors were characterized with respect to critical temperatures, critical currents, microstructure and composition of the superconducting and secondary phases. The samples were then analyzed by Moessbauer spectroscopy. Energy dispersive X-ray (EDX) analysis showed that both 57Fe and 151Eu were incorporated in the superconducting crystallites. Sn was found in secondary phases. Incorporation of Eu into the superconducting phase favored the formation of the Tl-1212 phase. The isomer shift and the electric field gradient derived from the 151Eu spectra were consistent with Eu3+ at the Ca site. The 57Fe Moessbauer spectra refer to two different micro-environments for the Fe3+. They were assigned to Fe3+ substituting Cu between the two Ca layers and between the Ca and Ba-Sr-O layers.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering