• Physical properties of the semiconducting delafossite AgNiO$_2$

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    • Keywords


      Delafossite AgNiO$_2$; hydrothermal method; semiconductor; optical properties; transport properties.

    • Abstract


      The delafossite AgNiO$_2$ was prepared by hydrothermal route. The X-ray diffraction shows a single phase indexed in a rhombohedral unit cell (R$\bar{3}m$) with a particle size of 12 nm. The Raman spectroscopy confirmed the singlephase. The thermal analysis shows a stability up to 290°C. The forbidden band (0.87 eV), determined from the diffuse reflectance, is assigned to the transition: Ag$^+$: 4d ${\rightarrow}$ hybridized (d$_{z2}$–s) – O$^{2–}$: 2p orbital. The magnetization M(H),measured at different temperatures, exhibits a low hysteresis at 200°C with a weak remanence of 495 Oe. It increases with the applied field to saturate at ${\sim}$5 kOe, suggesting a paramagnetism of AgNiO$_2$ nanocrystallites with a low spin (LS) Ni$^{3+}$ configuration. The thermal variation of the electrical conductivity indicates a semiconducting behaviour with an activation energy ($E_a$) of 0.013 eV. The high conductivity (${\sigma}_{300K}$ = 1.8 ${\Omega}^{–1}$ cm$^{–1}$) is in conformity with the non-cooperative effect of the Jahn–Teller Ni$^{3+}$ ion. The thermo-power shows p-type behaviour coming from oxygen intercalation in the layered lattice. The conduction occurs by polaron hopping between mixed valences Ag$^{2+/+}$ and increases with raising temperature, in agreement with a degenerate semiconductor. The valence band, determined from the capacitance measurements in KOH (0.1 M) electrolyte, is made up of Ag$^+$: 4d orbital, located at – 4.52 eV below vacuum.

    • Author Affiliations



      1. Laboratory of Electrochemistry-Corrosion, Metallurgy and Inorganic Chemistry, Faculty of Chemistry, USTHB, BP 32, 16111 Algiers, Algeria
      2. Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, USTHB, BP 32, 16111 Algiers, Algeria
    • Dates

  • Bulletin of Materials Science | News

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