Structural and physical properties relations of high temperature superconductors with a focus on mercury cuprates
- Czech Science Foundation (1999-2001)
Mercury cuprates HgBa2
(n = 1, 2, 3,...) are the last discovered family of high temperature superconductors. Their critical temperature 133 K is nowadays the highest and can be increased by 35 GPa up to 164 K. Their investigation is complicated by difficult preparation and insufficient resistance against ambient condition, in particular at higher members (n > 1). The aim of the project is to find optimum conditions for the mercury superconductors preparation in the form of ceramic materials as well as thin films. First it is the preparation of homogeneous and reactive precursors by the sol-gel method. Then it is the final synthesis in the closed system, sealed silica tubes, where the oxygen and mercury partial pressures can be adjusted by suitable agents with a help of multizone furnace. Appropriate partial pressures will be searched experimentally and by thermodynamic calculations. The semiempirical approach will be employed to analyse the relations between the superconducting and structural properties influenced by replacing of mercury by various cations and barium by strontium.
Crystal chemistry of the superconducting mercury cuprates
- Czech Science Foundation (1996-1998)
Mercury cuprates are recently discovered superconductors, structurally related to bismuth and thalium cuprates. The highest critical temperature among the family of superconducting cuprates and its steep increase with external pressure together with low anisotropy of the normal-state resistivity make them suitable candidates for fundamental research and technical applications. At the present, the main problem is the multiphase character of the materials. The project is directed to the search for conditions of synthesis of different members of HgBa2
and to their crystallographic and electric investigation.
Charge Carriers and Chemical Bond in Superconducting Oxides
- Czech Science Foundation (1993-1995)