Superconductivity above liquid nitrogen temperature: preparation and properties of a family of perovskite-based superconductors

On the Superconductivity Suppression in Eu1-xPrxBa2Cu3O7-δ

This article reports on the non-trivial suppression of superconductivity in the Eu1-xPrxBCO cuprates. As non-magnetic Eu3+ ions are replaced by Pr3+ carrying a magnetic moment, spin-related superconductivity loss can be expected. The research shows that the superconductivity disappearance for x > 0.4 results from depletion of the carriers and their localization. The above conclusion was drawn by low-temperature X-ray diffraction analysis showing increased characteristic phonon frequencies with Pr content. This mechanism should promote electron-phonon coupling, at least for acoustic phonons. However, the inverse phenomenon was detected. Namely, there is a gradual deterioration of the optical phonons responsible for vibration of the Cu-O bonds with Pr increasing, as evidenced by Raman spectroscopy. Furthermore, the results of X-ray absorption spectroscopy precisely showed the location of the carriers for Pr-rich specimens. Finally, a schematic diagram for Eu1-xPrxBCO is proposed to consolidate the presented research.

Neutron Diffraction Studies of High TC Superconductors

We have investigated the structure and composition of La2CuO4 (both pure and Sr-doped) and Nd(Ba2−xNdx)Cu3O7 using powder neutron diffraction. In La2−xSrxCuO4, Tc reacnes its maximum at x=0.15, after which vacancies are introduced in the 2D planes and superconductivity is destroyed. Superconductivity in La2CuO4 is not bulk. No evidence for nonstoichlometry in this material can be observed. In the Nd(Ba2−xNdx)Cu3O7 system, Tc is a complex function of oxygen ordering and electronic effects.

Studies on separation of rare earth elements on various types of anion-exchangers in the C3H7OH-7 M HNO3 systems

This paper presents the possibilities of separation of yttrium(III)-neodymium(III) and samarium(III)-neodymium(III) pairs by frontal analysis on strongly basic anion-exchangers Wofatit SBW, Wofatit SBK and Lewatit MP 5080 in the systems: 90% (v/v) 2-propanol-10% (v/v) 7 M HNO3 and 90% (v/v) 1-propanol-10% (v/v) 7 M HNO3. The best results are obtained on Lewatit MP 5080 in the 90% (v/v) 2-propanol-10% (v/v) 7 M HNO3 system. In this system, on 1 dm3 of this anion-exchanger, 1.95 kg yttrium(III) and 0.3 kg samarium(III) were purified decreasing the microcomponent content to below 10(-3)%.