Indium Perovskite-Like Phases: Synthesis, Crystal Structure Refinement, and Properties

Author： Afanasieva I.N. Kuzmicheva G.M. Mitin A.V. Khlybov E.P.

ISSN： 0022-4766

Source： Journal of Structural Chemistry, Vol.42, Iss.6, 2001-11, pp. : 967-981

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Abstract

This paper describes syntheses and structure and composition refinement for phases of the general composition (In,Cu)Sr_2YCu_2{rm O}_{6 + delta} (1212) and (In,Cu)(Sr,Ho)_2(Ho,Ce)_2{rm O}_{8 + delta} (1222) obtained in air atmosphere and for the same phases treated in oxygen. Oxygen treatment did not change the oxygen content in the phases, but changed the composition of the cationic (especially In) sites. The absence of superconductivity is explained by the nonoptimal values of the formal charge of copper [FC(Cu)] obtained from the electroneutrality condition and taking into account the refined phase compositions. Superconductivity found for the phase of composition (In,Cu)Ba_2(Y,Ca)Cu_2{rm O}_{6 + delta} (T_{rm c} = 80 K) is lost when the sample is annealed in air and during subsequent thermobaric treatment, leading to changes in the oxygen and indium contents and to a decrease in FC(Cu) from ∼2.15 to 2.05 and 2.08, respectively.