Metal-insulator transition in Ni-doped Na0.75CoO2: Insights from infrared studies
M Premila A Bharathi N Gayathri P Yasodha Y Hariharan C S Sundar
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Nickel substitution at the cobalt site in Na0.75CoO2 induces an upturn in the resistivity on lowering the temperature, with the metal-to-insulator transition temperature (TMIT) increasing with the Ni content. Low temperature far infrared measurements on polycrystalline samples of Na0.75CoO2 and Na0.75Co0.95Ni0.05O2, the latter having TMIT ∼ 175 K, have been carried out. Dramatic changes in the Na mode frequencies, and relative intensities of the out-of-plane modes corresponding to the two Na sites are observed, coincident with the MIT in Na0.75Co0.95Ni0.05O2. It is argued that these changes are associated with a charge ordering of the CoO2 layer, associated with the metal-insulator transition.
M Premila1 A Bharathi1 N Gayathri1 P Yasodha1 Y Hariharan1 C S Sundar1
Volume 96, 2022
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