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Search for superconducting materials of high critical temperature

19th national competition for scientific and technical research

High-temperature superconducting materials

Senior Researcher : Regino Sáez Puche

Research Centre or Institution : Instituto de Energía Solar. Universidad Politécnica de Madrid


The research project aims the search for high critical temperature (Tc) superconductors. Oxides with Cu in mixed valence states 2+/3+ (d8/d9) have been prepared and characterised. Synthesis methods include the unusual high pressure and high temperature technique. Chemical and structural details have been studied using synchrotron X-ray and neutron diffraction techniques, as well as muon spectroscopy. Throughout the project, the study of M1-xCuxSr2RCu2O7+x (R=rare earth and M=Fe and Mo) superconductors has been addressed. The partial substitution of Cu by other cations in high oxidation states, such as Fe3+/Fe4+ or Mo5+, gives rise to a high concentration of holes in the CuO2 planes. This study has led to the completion of three Doctoral Theses. Among the main results, Mo0.3Cu0.3Sr2TmCu2O7+d and FeSr2YCu2O7+d superconducting phases with high Tc (83K and 70K, respectively) are notable. In addition, the coexistence of superconductivity and magnetism in FeSr2YCu2O7.85 has been proven. In the final stage of the project, the search for superconductivity has focused on different transition metal cations with mixed valence. 

The recent discovery of superconductivity in Nd0.8Sr0.2NiO2 thin films has motivated the study of the family of nickelates (R1-xSrx)n+1NinO2n+1 (R= rare earth) as potential high Tc  superconductors. These oxides, are obtained via topotactic reduction of the Ruddlesden-Popper phases, (R1-xSrx)n+1NinO3n+1 with CaH2. The prepared materials, with composition R0.8Sr1.2NiO3, contain Ni in square-plane coordination forming infinite chains (spin-ladder) along the c axis and mixed valence Ni+(d9)/ Ni2+(d8), with similar features to cuprates, thus suggesting their potential behavior as high Tc superconductors.

Note: Professor Regino Saez Puche is the main researcher of this project, since the death of Mr. Emilio Morán, in April  2020.


Scientific Production
Magazine Articles 7
Communications at national conferences 7
Communications at international conferences 6


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