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Non-trivial valence states in high-Tc superconductors
Synthetic Metals, 41-43 (1991) 4059
NON-TRIVIAL
VALENCE
STATES
4059
IN H I G H - T ~
SUPERCONDUCTORS
Michael L. Khidekel' and E.N.Ezakovich Institute of Chemical Physics, Academy of Sciences USSR, Chernogolovka, 142432, Moscowskaja oblast' USSR
The oxidation states of elements Cu, Au, Ru and I in the I-2-3 superconducting system are being investigated in this paper. Thenmogravimetrical, X-ray phase and X-ray structural analyses alongside with local X-ray spectroscopy, XPS, IK- and MSssbauer spectroscopies were used to study the samples. Tc was measured against the resistance and magnetic properties changes down to liquid nitrogen and helium temperatures. A new compound (~I.4CUo+3)BaCu+205 containing Cu+2-Cu+3 and isostructural to Y2BaCuO 5 has been singled out. Also it has been proved that the latter compound in its polycrystalline sample alwaYs contains N 20% of Cu +3 ions. The Au doped samples superconduct only when containing Au+3 ions. The catalytical role of Ru in the I-2-3 synthesis has been stressed. A new Ru-containing phase in Y2Ba5CuRu2018(Ru+8) has been singled out. In the EuBa2Cu307_ [ (I06) x system x=0.029-0.15 mols. Iodine is present in its oxidation state +7. There are 3 regions of transition into superconducting state depending on the value of X at 87K, 60K and 28K. This in the I-2-3 system the elements are stabilized in their highest oxidation state: Cu+3, Au+3, Ru+8, I +7.
Elsevier Sequoia/Printed in The
Netherlands
NON-TRIVIAL
VALENCE
STATES
4059
IN H I G H - T ~
SUPERCONDUCTORS
Michael L. Khidekel' and E.N.Ezakovich Institute of Chemical Physics, Academy of Sciences USSR, Chernogolovka, 142432, Moscowskaja oblast' USSR
The oxidation states of elements Cu, Au, Ru and I in the I-2-3 superconducting system are being investigated in this paper. Thenmogravimetrical, X-ray phase and X-ray structural analyses alongside with local X-ray spectroscopy, XPS, IK- and MSssbauer spectroscopies were used to study the samples. Tc was measured against the resistance and magnetic properties changes down to liquid nitrogen and helium temperatures. A new compound (~I.4CUo+3)BaCu+205 containing Cu+2-Cu+3 and isostructural to Y2BaCuO 5 has been singled out. Also it has been proved that the latter compound in its polycrystalline sample alwaYs contains N 20% of Cu +3 ions. The Au doped samples superconduct only when containing Au+3 ions. The catalytical role of Ru in the I-2-3 synthesis has been stressed. A new Ru-containing phase in Y2Ba5CuRu2018(Ru+8) has been singled out. In the EuBa2Cu307_ [ (I06) x system x=0.029-0.15 mols. Iodine is present in its oxidation state +7. There are 3 regions of transition into superconducting state depending on the value of X at 87K, 60K and 28K. This in the I-2-3 system the elements are stabilized in their highest oxidation state: Cu+3, Au+3, Ru+8, I +7.
Elsevier Sequoia/Printed in The
Netherlands