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Percorrer por autor "Omari, L.H."

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  • The effect of transition metal substitution on the structural, elastic, optical, electrical and dielectric properties of M0.5Fe2·5O4 (M=Co and Mg) synthesized by the auto combustion method
    Publication . El Heda, Issa; Massoudi, Jalel; Dhahri, Radhia; Dhahri, Essebti; Bahri, Fathi; Omari, L.H.; Mariano, José
    Spinel nanoparticles M0.5Fe2.5O4 (M = Co,Mg) were elaborated by the auto-combustion method using glycine as a fuel. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy have been invested to investigate the structural and morphological properties of these compounds. The optical study reveals that these samples exhibit a strong absorption in the visible range. They possess intermediate gap energies 2.91 eV for Co0.5Fe2.5O4 and 3.16 eV for Mg0.5Fe2.5O4 which makes them good candidates in terms of photovoltaic applications. Electrical analysis demonstrates a semiconductor [300-520 K] -metallic [540-660 K] transition at 540 K. Correlated Barrier Hopping (CBH) and No Overlap Small Polaron Tunneling (NSPT) models dominate the conduction mechanisms in both compounds. The Nyquist diagrams are modelled by two series-connected circuits reflecting grain (Rg//Cg) and grain boundary effects (Rgb//CPEgb). Quantitative analysis of the dielectric constant is indicative that these compounds are promising at the level of electronic systems industry, LTCC devices and super capacitor applications.
    2023Artigo científico Desconhecido Ver mais
  • Theoretical study of magnetic and magnetocaloric properties and MCE modeling by the mean-field theory in CoFeCuO4 spinel ferrite
    Publication . Nasri, M.; Henchiri, C.; Dhahri, R.; Dhahri, E.; Omari, L.H.; Mariano, José
    In this research paper, we are basically interested in the theoretical investigation of magnetic and magnetocaloric properties of CoFeCuO4 spinel ferrite. Our sample was prepared using the sol-gel method. The XRD analysis confirmed the cubic spinel structure with the Fd (3) over barm space group exhibited by our compound. Furthermore, the positive slope detected in the Arrott plots is indicative of the second-order phase transition. Based on the phenomenological model of Hamad, the simulation of the magnetization M (T) goes in good agreement with the experimental results. Moreover, the magnetic entropy change (-Delta S-M) estimations by Hamad's model and Landau theory go in good accordance with the experimental results determined using Maxwell relations above the Curie-temperature T-C, and they show a divergence below this temperature. The relative cooling power (RCP) has a value of 64.342 J.kg(-1) under a magnetic field of 5T, which is suggestive that our compound can be a promising material for the magnetic refrigeration (MR) application. Finally, the validity of the mean-field theory to the theoretical study was proven through the compatibility inferred between the (-Delta S-M(max)) and RCP values obtained by the Maxwell relation and the Bean-Rodbell model.
    2022Artigo científico Desconhecido Ver mais