Synthesis and characterization of bulk <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Nd</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi>Ni</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Nd</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi>Ni</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
Bixia Wang, Hong Zheng, Elena Krivyakina, O. Chmaissem, Pietro Papa Lopes, J. W. Lynn, Leighanne C. Gallington, Yang Ren, Stephan Rosenkranz, J. F. Mitchell, Daniel Phelan
Abstract
Epitaxial ``infinite layer'' Nd${}_{1\ensuremath{-}x}$Sr${}_{x}$NiO${}_{2}$ thin films on SrTiO${}_{3}$ substrates may represent the realization of long-sought, cupratelike superconductivity in an isoelectronic Ni${}^{1+}$ oxide. Unfortunately, high quality bulk Ni${}^{1+}$ compounds are notoriously challenging to synthesize. In this work, the authors provide details of successful synthesis approaches to the bulk polycrystalline precursor Nd${}_{1\ensuremath{-}x}$Sr${}_{x}$NiO${}_{3}$, using soft chemistry followed by high-pO${}_{2}$ synthesis, and its subsequent reduction to the infinite layer compound. In situ x-ray diffraction is used to track the reduction pathway from NdNiO${}_{3}$ to NdNiO${}_{2}$ along with a structural model for Nd${}_{0.9}$Sr${}_{0.1}$NiO${}_{2}$ refined from neutron diffraction data. However, superconductivity remains elusive in bulk Nd${}_{1\ensuremath{-}x}$Sr${}_{x}$NiO${}_{2}$, potentially underscoring the important role of epitaxy in this new nickelate superconductor family.