# Metallic and Non-superconducting Phases in $LnBa_2Cu_{3-x}Ni_xO_{7 + \delta}$ Oxides$^1$

Manoharan, Sundar S and Ramesh, S and Hegde, MS and Subbanna, GN (1994) Metallic and Non-superconducting Phases in $LnBa_2Cu_{3-x}Ni_xO_{7 + \delta}$ Oxides$^1$. In: Journal of Solid State Chemistry, 112 (2). pp. 281-287.

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## Abstract

A series of compounds $LaBa_2Cu_{3-x}Ni_xO_{7 \pm\delta}$ (0.0 < x < 0.3) and $LnBa_2Cu_{3-x}Ni_x0_{7- \delta}$ (Lnl23; Ln = Pr, Nd, Sm, Gd, and Er; x = 0.1, 0.2) has been synthesized by a ceramic method and their structure characterized by X-ray and electron diffraction. The substitution of nickel in $LaBa_2Cu_3O_{7 \pm\delta}(Lal23)$ induces an orthorhombic to tetragonal structural transition as well reducing the activation energy for oxygen desorption. Orthorhombicity increased with decreasing lanthanide ton radius in the $LnBa_2Cu_{2.9}Ni_{0.1}O_{7 \pm\delta}$ system. Electrical resistivity measurements show metallic behavior down to 4.2 K for $LaBa_2Cu_{3-x}Ni_xO_{7 \pm\delta}$ (0.1 < x < 0.3). The superconducting transition temperatures of Ni-doped Lnl23 decreased with increasing rare earth ion radius, for the same nickel content. These properties are discussed in terms of the $Ni^{3+}$ ion occupying the Cu(l) sites in La 123 stabilized by a larger $La^{3+}$ ion and $Ni^{2+}$ ion occupying the Cu(2) sites in the Lnl23 system of oxides.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Division of Chemical Sciences > Materials Research CentreDivision of Chemical Sciences > Solid State & Structural Chemistry Unit 25 Sep 2006 19 Sep 2010 04:32 http://eprints.iisc.ernet.in/id/eprint/8721