• A K KUSHWAHA

      Articles written in Bulletin of Materials Science

    • A study on the vibrational frequencies, elastic properties and sound velocities of vanadium spinel oxides AV$_2$O$_4$ (A $=$ Mn, Fe and Zn) short-range non-Coulomb potential theoretical model

      A K KUSHWAHA R KHENATA A BOUHEMADOU S AKBUDAK R AHMED

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      Owing to the fact of the AB$_2$O$_4$ spinel oxide’s chemical and thermal stability, and other intriguing properties make them suitable candidate materials for many applications, including chemical looping and catalytic reactions. To do our investigations, a short-range non-Coulomb potential theoretical model is used to calculate the zone-centre, elastic constants, infrared phonon mode frequencies, Raman phonon mode frequencies, velocities of the sound wave along the highly symmetric three crystallographic-axes and Debye temperature of the vanadium spinel oxides AV$_2$O$_4$ (A $=$ Mn, Fe and Zn). The preliminary results of our calculations show that the interaction inthe second neighbour (V–O) is much stronger than the interaction of the first neighbour (A–O). Moreover, from the analysis of the obtained results of elastic constants, the nature of the studied vanadium spinels are found to beductile.

    • Metal to semiconductor transition and figure of merit enhancement of Li$_2$CuAs compound by Na substitution

      M MOUTASSEM T SEDDIK D E SI MOHAMMED M BATOUCHE H KHACHAI R KHENATA R AHMED V SRIVASTAVA A BOUHEMADOU A K KUSHWAHA S BIN OMRAN

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      In this study, an analysis of the effect of Na substitution on the electronic, structural and thermoelectric (TE) properties of the Li$_2$CuAs material is presented. The study is performed by employing the full-potential linearized augmented plane wave plus local orbital method designed within the density functional theory. To carry out the calculations related to the band structure, generalized gradient approximation by Wu-Cohen (WC-GGA) in combination with Trans Blaha-modified Becke-Johanson mBJ (TB-mBJ) potential is employed. Our results at the level of the WC-GGA approach show that there is no bandgap, whereas, at the level of the TB-mBJ approximation, the material displays bandgap with Na substitution, which is found to be further increased with the increasing Na concentration. To understand the role of different electronic states on the bandgap structure, the total and partial densities of states are also analysed. Furthermore, the temperature effect on the Seebeck coefficient, electronic thermal conductivity, electrical conductivity, power factor and figure of merit are computed. Our obtained results of the TE properties of Li$_2$CuAs at different Na compositions suggest that this compound is a potential candidate for thermoelectricity.

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      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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