Transitions Between Lanthanum Cuprates: Crystal Structures of T′, Orthorhombic, and K2NiF4-type La2CuO4

Authors

  • Roland Hord,

    1. Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt
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  • Gerhard Cordier,

    1. Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt
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  • Kathrin Hofmann,

    1. Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt
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  • Alexander Buckow,

    1. Institut für Materialwissenschaften, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt
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  • Gwendolyne Pascua,

    1. Laboratory for Muon Spin Spectroscopy, Paul-Scherrer-Institute (PSI), 5232 Villigen, Switzerland
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  • Hubertus Luetkens,

    1. Laboratory for Muon Spin Spectroscopy, Paul-Scherrer-Institute (PSI), 5232 Villigen, Switzerland
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  • Prof. Dr. Lambert Alff,

    Corresponding author
    1. Institut für Materialwissenschaften, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt
    • Institut für Materialwissenschaften, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt
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  • Prof. Dr. Barbara Albert

    Corresponding author
    1. Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt
    • Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt, Fax: +49-6151-166029
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  • Dedicated to Professor Hanskarl Müller-Buschbaum on the Occasion of His 80th Birthday

Abstract

Through low-temperature synthesis in CsOH flux, lanthanum cuprate La2CuO4 can be obtained in a metastable form, the so-called T′ modification (tetragonal, I4/mmm, no. 139, a = 400.95(2) pm, c = 1254.08(7) pm). When heated, this T′ phase transforms into a K2NiF4-type modification, whose crystal structure was now refined from X-ray powder data (tetragonal, I4/mmm, no. 139, a = 383.29(3) pm, c = 1331.3(2) pm at T = 1073 K). The well-known orthorhombic phase (s.g. Cmce, no. 64, a = 536.14(3) pm, b = 1315.53(8) pm, c = 540.20(3) pm) – usually obtained via conventional solid state synthesis – was observed to form upon cooling from the K2NiF4-type modification. High-temperature powder diffractometry allowed crystal structure refinements for all of the three phases.

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