Redox response model for partly substituted cuprates

Óesterreicher, H.

doi:10.1016/0025-5408(94)90036-1

Cited by 9 publications

(2 citation statements)

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“…Similarly to A = Ba analogues, superconductivity for Sr-based systems develops on reducing steps in the preparations as a result of U state clustering [17,18]. On reoxidation, the Fe maintain the clustered state and convert to a (1)5 configuration.…”

Section: Discussionmentioning

confidence: 99%

“…Factors which have an influence in determining hole concentration are connected [17] with the various modes of inhomogeneous (cluster) M substitution. One can understand these influences in a local thermodynamic model [18] which considers the enthalpy of various local configurations denoted by n(m) where n corresponds to the Cu site and m to the oxygen coordination. Accordingly, for a given y, or the related incremental enthalpy of oxide desorption H * (asterisk denotes quantity per mole of O 2 ), there exist several important influences.…”

Section: Introductionmentioning

confidence: 99%

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Superconductivity through redox treatments of

O’Brien¹,

Óesterreicher²

1998

Supercond. Sci. Technol.

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Superconductivity is developed through controlled redox treatment variation in a material with unusually high Fe concentration. The dependence of the structural, magnetic, and superconductive properties of ; x = 0.13 or x = 0.167) on annealing conditions is explored. Sintered bulk materials are prepared with an extended exposure at T = 1000 K. This procedure is designated OP for oxygenating preparation and all materials treated in this way show no signs of superconductivity above 5 K. Subsequently, Gd getter annealing is used to control reductions at T = 1000 K for 4 days followed by reoxidation at 800 K for 1 h. For x = 0.167 and z = 0, a strong reduction (y = 6.3) reoxidation procedure resulted in the development of superconductivity with . As the Ca content increases, successively milder reductive conditions must be employed to obtain superconductors. A local thermodynamic model based on the stabilities of various Fe cluster arrangements and oxidative states predicts the changes expected on Ca substitution. It is argued that Fe in a cluster with 5-fold O coordination is not detrimental to superconductivity while 4-fold coordination quenches holes because of the uncompensated nature of this low O coordination.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%