• TAPAS KUMAR MANDAL

      Articles written in Bulletin of Materials Science

    • Multifunctional properties of ceria nanocubes synthesized by a hydrothermal method

      R V LAKSHMI KAMALESH PAL TAPAS KUMAR MANDAL S T ARUNA

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      Nanosized ceria is an extremely versatile and commercially valuable material because of its industrially impor-tant applications. The present work describes the synthesis of ceria nanocubes by a simple hydrothermal method. The size of the synthesized ceria nanocubes are 8–20 nm. The formation of ceria phase has been corroborated by X-ray photoelec-tron spectroscopy and X-ray diffractometry. Selected area electron diffraction patterns obtained for the nanocubes are also precisely indexed to the cubic ceria phase. The synthesized ceria nanocubes exhibit a high surface area of 26 m² g⁻¹ and also high catalytic activity. The work also investigates the influence of ceria nanocubes on the corrosion resistance of sol–gel hybrid coatings in 3.5% NaCl solution on AA2024 substrates. The corrosion behaviour of the sol–gel coatings revealed that ceria nanocubes reinforce the barrier properties of the sol–gel coatings and confer longer active protection to the metallic substrate.

    • Investigation of multiferroic behaviour at room temperature in Bi-induced orthoferrite: combined experimental and first principles studies

      KUMARI NAVEEN NIKHIL KUMAR SONIA RANI TAPAS KUMAR MANDAL ANURAG GAUR P D BABU VASUDEVA SIRUGURI PRADIP K MAJI SUDIPTA KANUNGO AVIJIT KUMAR PAUL

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      Perovskite oxides are an important and exciting class of materials owing to the structural diversity with remarkable magnetic, optical and electronic behaviours. Here, a single-phase multiferroic orthoferrite, Y$_{0.74}$Bi$_{0.25}$FeO$_{2.97}$ (YBFO), has been synthesized by a conventional solid-state method. The crystal structure was refined using the Rietveld refinement method from powder X-ray diffraction data, and confirms an orthorhombic structure with the Pnma space group. The Curie-Weiss fitting to the magnetic susceptibility shows that the $\theta$-value is $–$926 K and $\mu_{\rm eff} = 5.59$ $\mu_{\rm B}$, exhibiting canted antiferromagnetism. Room temperature magnetic and ferroelectric hysteresis loops verify the presence of magnetic as well as ferroelectric ordering in the material with a remnant polarization ($P_{\rm r}$) of 0.27 $\mu$C cm$^{–2}$ and electric coercivity ($E_{\rm c}$) of 15 kV cm$^{–1}$. Temperature-dependent $P–E$ loops and pyrocurrent response confirm the inherent multiferroic nature of the material. The UV–visible study indicates a semiconductor nature with the bandgap of 1.86 eV. Density-functional theory calculations support the observed experimental behaviour and it signified the role of Bisubstitution. Even a very less concentration of Bi-doping can form an exciting room temperature multiferroic material.

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