A. K. Deb
Raiganj College (University College)
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Featured researches published by A. K. Deb.
Journal of Physics: Condensed Matter | 2007
S. Chatterjee; S. Giri; S. Majumdar; A. K. Deb; S. K. De; V Hardy
We present here a detailed investigation of the magnetic and structural behaviours of a ferromagnetic shape memory alloy with nominal composition Ni2Mn1.44Sb0.6. The alloy undergoes a structural transition from a high-temperature cubic phase () to an orthorhombic low-temperature phase below approximately 200 K. We observe a clear signature of this martensitic transformation in resistivity, magnetic susceptibility, heat capacity and x-ray diffraction data. The first-order nature of the transition is clear from the thermal irreversibility present in the temperature dependence of various physical properties. A wide region of phase coexistence across the martensitic transformation, arising from the influence of disorder on the first-order phase transition, is observed. A small but positive entropy change due to an applied magnetic field occurs across the region of phase coexistence. An interplay between the structural and magnetic behaviour is evident from our study.
Journal of Applied Physics | 2012
K. Malik; Diptasikha Das; Dibyendu Mondal; Dipankar Chattopadhyay; A. K. Deb; S. Bandyopadhyay; Aritra Banerjee
Polycrystalline Bi1−xSbx alloys have been synthesized over a wide range of antimony concentration (0.08 ≤ x ≤ 0.20) by solid state reaction method. In depth structural analysis using x-ray diffraction (XRD) and temperature dependent resistivity (ρ) measurement of synthesized samples have been performed. XRD data confirmed single phase nature of polycrystalline samples and revealed that complete solid solution is formed between bismuth and antimony. Rietveld refinement technique, utilizing maud software, has been used to perform detailed structural analysis of the samples and lattice parameters of polycrystalline Bi1−xSbx alloys have been estimated. Lattice parameter and unit cell volume decreases monotonically with increasing antimony content. The variation of lattice parameters with antimony concentration depicts a distinct slope change at x = 0.12. Band gap (Eg) has been estimated from the thermal variation of resistivity data, with the 12% Sb content sample showing maximum Eg. It has been observed that...
Journal of Applied Physics | 2015
Diptasikha Das; K. Malik; A. K. Deb; S. Dhara; S. Bandyopadhyay; Aritra Banerjee
Structural and thermoelectric properties of metallic and semiconducting Sb2Te3 are reported. X-Ray diffraction and Raman spectroscopy studies reveal that semiconducting sample has higher defect density. Nature and origin of possible defects are highlighted. Semiconducting Sb2Te3 hosts larger numbers of defects, which act as scattering center and give rise to the increased value of resistivity, thermopower, and power factor. Thermopower data indicate p-type nature of the synthesized samples. It is evidenced that the surface states are often mixed with the bulk state, giving rise to metallicity in Sb2Te3. Role of different scattering mechanism on the thermoelectric property of Sb2Te3 is discussed.
Journal of Applied Crystallography | 2010
Sujit Manna; Tandra Ghoshal; A. K. Deb; S.K. De
Nanoparticles of the cubic phase of zirconia (ZrO2) of size range 4.5–8.7 nm have been synthesized by alkaline hydrolysis of a zirconium salt followed by solvothermal reaction. Subsequently, the room-temperature stability of cubic ZrO2 nanoparticles has been explored with the goal of understanding how crystal structure tends to transform into a structure of higher symmetry with decreasing crystallite size. The room-temperature-stable cubic phase in nanosized ZrO2 has been observed to transform into the monoclinic phase at 873 K. The crystalline phases of ZrO2 nanocrystals have been determined quantitatively by Rietveld refinement. Lattice constant and internal strain increase with decreasing particle size. Growth kinetics studies have established that cubic nanocrystals are more stable at smaller crystallite sizes. UV–visible absorption spectra show an absorption peak at 275 nm which indicates a lowering of the band gap energy. Photoluminescence spectra of zirconia nanoparticles show an emission peak at 305 nm at room temperature. The modification of the optical properties is explained on the basis of oxygen vacancies present within the samples.
Applied Physics Letters | 2013
K. Malik; Diptasikha Das; S. Bandyopadhyay; P. Mandal; A. K. Deb; Velaga Srihari; Aritra Banerjee
Thermal variation of structural property, linear thermal expansion coefficient (α), resistivity (ρ), thermopower (S), and power factor (PF) of polycrystalline Bi1-xSbx (x = 0.10 and 0.14) samples are reported. Temperature-dependent powder diffraction experiments indicate that samples do not undergo any structural phase transition. Rietveld refinement technique has been used to perform detailed structural analysis. Temperature dependence of α is found to be stronger for Bi0.90Sb0.10. Also, PF for direct band gap Bi0.90Sb0.10 is higher as compared to that for indirect band gap Bi0.86Sb0.14. Role of electron-electron and electron-phonon scattering on ρ, S, and PF has been discussed.
EPL | 2016
Diptasikha Das; K. Malik; A. K. Deb; V.A. Kulbachinskii; V. G. Kytin; S. Chatterjee; S. Dhara; S. Bandyopadhyay; Aritra Banerjee
Polycrystalline Sb2Te3−x Se x samples were synthesized by the solid-state reaction method. The structural analysis showed that up to the maximal concentration of Se, the samples possess rhombohedral crystal symmetry (space group ). The increase of Se content increases the resistivity of the samples. The variation of phonon frequencies, observed from the Raman spectroscopic study, depicts an anomalous behaviour around . The sample Sb2Te2.8Se0.2 also shows maximum Seebeck coefficient, carrier concentration and thermoelectric power factor. The nature of the scattering mechanism controlling the thermopower data has been explored. The thermoelectric properties of the synthesized materials have been analyzed theoretically in the frame of the Boltzmann equation approach.
DAE SOLID STATE PHYSICS SYMPOSIUM 2016 | 2017
Subarna Das; Pintu Singha; S. Bandyopadhyay; V.A. Kulbachinskii; A. K. Deb; Aritra Banerjee
Sb2Te3 + x% Mn (x=0.0, 0.1) nanocomposites were synthesized by ball milling method. Structural characterizations are carried out at room temperature using X-Ray Diffraction (XRD) technique. Williamson-Hall method is employed to study the effect of Mn on the lattice strain of the Sb2Te3 sample. Thermal variation of resistivity [ρ(T)] measurement, performed down to 10 K, shows that resistivity decreases with incorporation of Mn. Temperature dependent thermopower [S(T)], measured in temperature range 300 K – 20 K, reveals that both the samples are p-type in nature. Thermoelectric Power Factor (PF=S2/p) increases with incorporation of Mn.
DAE SOLID STATE PHYSICS SYMPOSIUM 2016 | 2017
Pintu Singha; Subarna Das; S. Bandyopadhyay; V. A. Kulbashinskii; A. K. Deb; Aritra Banerjee
Bi2Te3+x% Graphite nanocomposite samples were synthesized by ball milling method. Structural characterizations are carried out at room temperature using X-Ray Diffraction (XRD) technique. Lattice strain, as calculated from the XRD data, increases with increasing graphite content. Thermal variation of resistivity data, measured down to 10K, shows that all the nanocomposite samples are semiconducting in nature. Activation energy of the samples estimated from the resistivity data, increases with increasing graphite concentration.
EPL | 2016
K. Malik; Diptasikha Das; A. K. Deb; V.A. Kulbachinskii; Velaga Srihari; S. Bandyopadhyay; Aritra Banerjee
Temperature-dependent structural studies of polycrystalline Bi1−x Sb x alloys were carried out using synchrotron x-ray diffraction. In-depth powder diffraction analysis reveals that an iso-structural phase transition takes place in the rhombohedral Bi-Sb alloy around 200 K, which is accompanied by anomalous behavior in the temperature-dependent linear thermal expansion data. In addition, the thermal variation of refined isotropic thermal parameters or Debye-Waller factor (B iso), ratio of the lattice parameters and Debye temperature indicates that anisotropy, arising due to local structural disorder, plays a significant role in this material.
DAE SOLID STATE PHYSICS SYMPOSIUM 2015 | 2016
Diptasikha Das; K. Malik; A. K. Deb; Arup Dasgupta; S. Bandyopadhyay; V. A. Kulbashinskii; Aritra Banerjee
In depth structural analysis of the polycrystalline Sb2Te3-xSex alloy has been done by Rietveld refinement technique using MAUD software. Thermal variation of resistivity measurement is performed down to 10 K. Temperature dependent thermopower, measured in the range 300-20 K, reveals that samples are p-type in nature. Power factor has been estimated using resistivity and thermopower data.