Chemical pressure and other effects of strontium substitution in YBa2Cu3O9−δ

doi:10.1016/0022-4596(91)90242-A

Journal of Solid State Chemistry

Volume 92, Issue 1, May 1991, Pages 57-67

https://doi.org/10.1016/0022-4596(91)90242-A Get rights and content

Abstract

High quality samples of the Y(Ba_1−ySr_y)₂Cu₃O_6.948(6) solid solution phase were prepared via citrate gels by mixing the components on an atomic level. The range of solid solubility is 0.00 ≤ y ≤ 0.35(3) for a 910°C firing temperature and constant oxygen content, as determined by iodometry. At standardized conditions, the limiting phase with y = 0.35(3) is in equilibrium with Y₂(Ba_0.9Sr_0.1)CuO₅ and (Sr, Y)₁₄Cu₂₄O₄₁, and the situation is described in terms of a tetrahedral four-component phase diagram. The slightly enhanced (anisotropic) contraction along the c axis of the unit cell, observed upon introduction of the smaller Sr atoms, is associated with apical compression of the coordination square pyramids of copper. Both the volume contraction and its anisotropy can be compared with the effects of applied pressure. In terms of chemical pressure $P∗ = ε · y$ , coefficients of ε_V = 6.8(2) GPa or ε_{D_t} = 2.4(4) GPa are obtained, depending on whether ε is deduced from unit cell volume V or its (tetragonal) distortion D_t. The responses of the superconducting state upon the applied and chemical pressure (the latter exerted at the Ba site) are, however, quite different, with $ΔT_{c} ΔP = 0.7 K/GPa$ and $ΔT_{c} Δy = −20(2) K$ . A specific feature must hence either be introduced by the real pressure (e.g., increase in carrier concentration) or by the chemical pressure [e.g., local strain effects and/or redistribution of oxygen around Cu(1) site].

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Regular articleChemical pressure and other effects of strontium substitution in YBa2Cu3O9−δ

Abstract

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Mater. Res. Bull.

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Solid State Commun.

Phys. Lett. A

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Physica C (Amsterdam)

Phys. Rev. B: Condens. Matter

Acta Chem. Scand.

Z. Kristollogr.

Appl. Phys. Lett.

Jpn. J. Appl. Phys., Part 2

Jpn. J. Appl. Phys., Part 2

Jpn. J. Appl. Phys., Part 2

J. Appl. Phys.

Regular article
Chemical pressure and other effects of strontium substitution in YBa₂Cu₃O_9−δ