Characterization and Characteristics of mechanochemically synthesized amorphous fast ionic conductor 50 SISOMO (50AgI-25Ag2O-25MoO3)

Mechanochemically synthesized amorphous 50SISOMO [50AgI-25Ag_2O-25MoO_3] fast ionic conductor shows high ionic conductivity of ~ 6x10^-3 {\Omega}^-1 cm-1 at room temperature. The highest ionic conductivity is achieved for 36 h milled sample, which is more than three orders of magnitude higher than that of crystalline AgI at room temperature. The samples are thermally stable at least up to ~70 {\deg}C. Thermoelectric power studies on 50 SISOMO amorphous fast ionic conductors (a-SIC) have been carried out in the temperature range 300-330K. Thermoelectric power (S) is found to vary linearly with the inverse of the absolute temperature, and can be expressed by the equation -S = [(0.19 \times 10^3/T) + 0.25] mV/K. The heat of transport (q*) of Ag+ ion i.e. 0.19 eV is nearly equal to the activation energy (E) i.e. 0.20 eV of Ag+ ion migration calculated from the conductivity plots indicating that the material has an average structure. This is also in consonance with earlier theories on heats of transport of ions in ionic solids.Comment: Presented in the "National Symposium on Advances in Material Science" held at Gorakhpur, India during 17-19 March 200

Effect of Zn doping on the Magneto-Caloric effect and Critical Constants of Mott Insulator MnV2O4

X-ray absorption near edge spectra (XANES) and magnetization of Zn doped MnV2O4 have been measured and from the magnetic measurement the critical exponents and magnetocaloric effect have been estimated. The XANES study indicates that Zn doping does not change the valence states in Mn and V. It has been shown that the obtained values of critical exponents \b{eta}, {\gamma} and {\delta} do not belong to universal class and the values are in between the 3D Heisenberg model and the mean field interaction model. The magnetization data follow the scaling equation and collapse into two branches indicating that the calculated critical exponents and critical temperature are unambiguous and intrinsic to the system. All the samples show large magneto-caloric effect. The second peak in magneto-caloric curve of Mn0.95Zn0.05V2O4 is due to the strong coupling between orbital and spin degrees of freedom. But 10% Zn doping reduces the residual spins on the V-V pairs resulting the decrease of coupling between orbital and spin degrees of freedom.Comment: 19 pages, 9 Figures. arXiv admin note: substantial text overlap with arXiv:1311.402

Magnetic Characteristics of High Entropy Alloys

High entropy alloy (HEA) is a multi-principal alloy having at least five principal elements in the concentration range of 5–35 at.%. HEAs having excellent mechanical properties and further these properties can be altered by the addition of different alloying element. For example with the addition of Al in base alloy make them a ductile and the addition of Co, Ti, etc. transforms base alloy to brittle material. This characteristic of HEAs makes them a promising technologically important material. A soft magnetic material should have good mechanical property, structural stability at high temperature and low coercivity with high magnetization. Recently, reported FeCoNiMn0.25Al0.25 and CoCrFeNiM (M = Cu, Mn) HEAs got attention as a better soft magnetic material because these HEAs having good soft magnetic characteristics along with good mechanical and excellent structural stability at high-temperature. Recent reports described that the mechanical as well as magnetic characteristics of these alloys can be tuned by the variation and/or the addition of alloying element in the base alloys. The magnetic characteristics of these alloys basically depend on the alloying element and compositional variation of the magnetic element present in particular HEAs. We have summarized the key results of magnetic characteristics of some recently investigated promising high entropy alloys

Experimental and computational approaches to study the high temperature thermoelectric properties of novel topological semimetal CoSi

Here, we study the thermoelectric properties of topological semimetal CoSi in the temperature range $300-800$ K by using combined experimental and density functional theory (DFT) based methods. CoSi is synthesized using arc melting technique and the Rietveld refinement gives the lattice parameters of a = b = c = 4.445 {\AA}. The measured values of Seebeck coefficient (S) shows the non-monotonic behaviour in the studied temperature range with the value of $\sim-$81 $\mu$V/K at room temperature. The $|S|$ first increases till 560 K ($\sim-$93 $\mu$V/K) and then decreases up to 800 K ($\sim-$84 $\mu$V/K) indicating the dominating n-type behaviour in the full temperature range. The electrical conductivity, $\sigma$ (thermal conductivity, $\kappa$) shows the monotonic decreasing (increasing) behaviour with the values of $\sim$5.2$\times 10^{5}$ (12.1 W/m-K) and $\sim$3.6$\times 10^{5}$ (14.2 W/m-K) $\Omega^{-1}m^{-1}$ at 300 K and 800 K, respectively. The $\kappa$ exhibits the temperature dependency as, $\kappa \propto T^{0.16}$. The DFT based Boltzmann transport theory is used to understand these behaviour. The multi-band electron and hole pockets appear to be mainly responsible for deciding the temperature dependent transport behaviour. Specifically, the decrease in the $|S|$ above 560 K and change in the slope of $\sigma$ around 450 K are due to the contribution of thermally generated charge carriers from the hole pockets. The temperature dependent relaxation time is computed which shows temperature dependency of $1/T^{0.35}$. Present study suggests that electronic band-structure obtained from DFT provides reasonably good estimate of the transport coefficients of CoSi in the high temperature region of $300-800$ K