Scientific Activities at the Solid State Chemistry Group
Iron based superconductors
Synthesis, crystal growth, structural and superconducting properties of the family of alkali metal intercalated iron chalcogenides with TC around 30K are investigated. A novel superconducting compound intercalated with Li and organic spacer between superconducting FeSe layers and TC~30K was recently synthesized in the group.
Crystallization of complex oxides by Traveling Solved Floating Zone (TSFZ)
Numerous complex oxide materials have been successfully crystallized by TSFZ method. This includes cuprates, manganates, orthoferrites, cobaltites and molecular magnets like SrCu2(BO3)2 and BiCu2PO6. Most of these crystals have volume of a few cm3 and are used for investigation of different physical properties using large facility instruments at Paul Scherrer Institute and at other scientific institutes.
Crystallization of intermetallic compounds by Flux and Bridgman method
Spin-Fluctuations were studied by neutron scattering in big single crystals (cm3) of a ternary stannide superconductor Ca3Ir4Sn13 grown in our group by a flux method. Bismuth selenide (Bi2Se3) is an example of topological insulators, which becomes a superconductor by intercalation with copper and performs magnetic ordering by doping with iron. We have grown single crystal of undoped, Cu-intercalated and Fe-doped bismuth selenide using a modified Bridgman method for µSR (muon spin rotation) and neutron scattering studies.
Complex oxides of 3d and 5d transition metals
Multiferroic materials with coupled magnetic order and ferroelectricity at already room temperature are investigated in this project. Complex perovskite oxides based on 3d transition metals (like RBaCuFeO5 or R2Cu2O5 where R-rare earth) both in form of powder or single crystals are of the interest. Growth of single crystalline samples of the 5d transition metal oxides of a sufficient size has to be developed to enable investigations and verification of theoretical models of a novel type of the Mott ground state. Synthesis of new materials in the iridate, molybdate and osmate series by solid state reactions is attempted. Flux and image furnace growth techniques are used to obtain single crystals
Oxygen thermodynamics and diffusion
For oxygen nonstoichiometric compounds studies of the oxygen content influence on physical properties are crucial (comp. e.g. superconductivity in cuprates and magnetoresistivity in manganates). From the solid state chemistry point of view, thermodynamics of the oxygen in the oxides (occupied sites/oxygen vacancies equilibrium, point defect equilibrium), oxidation/reduction kinetics (diffusion in solid state, surface reactions) and oxygen tracer diffusion (isotope exchange) are of the great scientific interests.