Structural Properties and Oxygen Stoichiometry of (Pr1.5Ce0.5)Sr2Cu2TaO10−δand (R1.5−xPrxCe0.5)Sr2Cu2NbO10−δ,R=Nd, Sm, Eu: Correlations with Electronic and Magnetic Properties

✍ Scribed by T.J. Goodwin; H.B. Radousky; R.N. Shelton

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 877 KB
• Volume: 133
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7509

✦ Synopsis

The structural parameters, phase purity, and oxygen stoichiometry of the (Pr 1.5 Ce 0.5 )Sr 2 Cu 2 TaO 10؊ and (R 1.5 ؊ x Pr x Ce 0.5 ) Sr 2 Cu 2 NbO 10؊ , R ‫؍‬ Nd, Sm, Eu, compounds are investigated with powder X-ray diffraction (XRD), Rietveld refinements, and thermogravimetric analysis (TGA). The XRD data indicate that all the (R 1.5؊x Pr x Ce 0.5 )Sr 2 Cu 2 NbO 10؊ compounds are isostructural and typically 98% pure. Rietveld refinements reveal a contraction of the c lattice parameter and features in the rare earth-planar oxygen bond length (as functions of Pr doping) that are correlated with the unusual electronic and magnetic transitions induced by the Pr ion in these materials. Results for deoxygenated samples show that the lattice expands upon deoxygenation and suggest that the oxygen is removed primarily from the SrO layers. TGA results reveal reliable techniques for determining oxygen stoichiometries and deoxygenating these compounds and that these compounds are oxygen deficient with 's of typically 0.045. The structural features of these compounds are compared to similar high T C cuprates, and related to the electronic and magnetic transitions and the suppression of superconductivity induced by the Pr ion in these materials. We discuss our results in terms of the current understanding of high T C cuprates and models for the suppression of superconductivity by the Pr ion in the related (R 1؊x Pr x )Ba 2 Cu 3 O 7 system.