Sourish Banerjee

Bio: Sourish Banerjee is an academic researcher from University of Calcutta. The author has contributed to research in topic(s): Magnetization & Cadmium selenide. The author has an hindex of 3, co-authored 5 publication(s) receiving 21 citation(s).

Structural and AC conductivity study of CdTe nanomaterials

Abstract: Cadmium telluride (CdTe) nanomaterials have been synthesized by soft chemical route using mercapto ethanol as a capping agent. Crystallization temperature of the sample is investigated using differential scanning calorimeter. X-ray diffraction and transmission electron microscope measurements show that the prepared sample belongs to cubic structure with the average particle size of 20 nm. Impedance spectroscopy is applied to investigate the dielectric relaxation of the sample in a temperature range from 313 to 593 K and in a frequency range from 42 Hz to 1.1 MHz. The complex impedance plane plot has been analyzed by an equivalent circuit consisting of two serially connected R-CPE units, each containing a resistance ( R ) and a constant phase element (CPE). Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The frequency dependence of real and imaginary parts of dielectric permittivity is analyzed using modified Cole–Cole equation. The temperature dependence relaxation time is found to obey the Arrhenius law having activation energy ~0.704 eV. The frequency dependent conductivity spectra are found to follow the power law. The frequency dependence ac conductivity is analyzed by power law.

Magnetic and dielectric study of Fe-doped CdSe nanoparticles

Abstract: Nanoparticles of cadmium selenide (CdSe) and Fe (5% and 10%) doped CdSe have been synthesized by soft chemical route and found to have cubic structure. The magnetic field dependent magnetization measurement of the doped samples indicates the presence of anti-ferromagnetic order. The temperature dependent magnetization (M-T) measurement under zero field cooled and field cooled conditions has also ruled out the presence of ferromagnetic component in the samples at room temperature as well as low temperature. In order to estimate the anti-ferromagnetic coupling among the doped Fe atoms, an M-T measurement at 500 Oe has been carried out, and the Curie-Weiss temperature θ of the samples has been estimated from the inverse of susceptibility versus temperature plots. The dielectric relaxation peaks are observed in the spectra of imaginary part of dielectric constant. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy ~ 0.4 eV for Fe doped samples. The frequency dependent conductivity spectra are found to obey the power law.

Electronic structure and transport properties of antiferromagnetic double perovskite Y2AlCrO6

Abstract: The antiferromagnetic G-type magnetic ordering in Y2AlCrO6 (YAC) has been investigated by electronic band structure calculations. The material is synthesised by a sol–gel technique and the electronic structure calculations are initiated by the experimental lattice parameters, obtained from the Rietveld refinement of the X-ray diffraction data. The Rietveld refinement shows that the room-temperature crystal structure of YAC is monoclinic with the space group P21/n, and contains an ordered array of alternating AlO6 and CrO6 octahedra tilted along the three pseudocubic axes according to the Glazer notation a−a−b+. The Raman spectrum of the sample is observed for P21/n symmetry. The field cooled and zero field cooled measurements of the sample are performed at a magnetic field of 100 Oe in the temperature range from 5 to 300 K. The temperature dependent magnetization shows the anti-ferromagnetic ordering of Cr ions in YAC. The calculated magnetic moment is well matched with the experimental magnetic moment and suggests the 3+ oxidation state of Cr with the canted alignment of its spin. The octahedral co-ordination of Cr3+ ions in YAC is confirmed from the photoluminescence spectrum. The band gap obtained from the diffuse reflectance measurements shows the semiconducting nature of the material. To observe the effect of grains, grain-boundaries and electrodes in the conduction process, the dielectric relaxation of YAC has been investigated using alternating current impedance spectroscopy in the frequency range from 50 Hz to 5 MHz as a function of temperature. An electrical equivalent circuit consisting of the resistance and the constant phase element is used to explain the impedance data. The observed results are used to discuss the effect of substitution of Cr by Al in the parent compound YCrO3.

Magnetic study of Co-doped CdSe nanoparticles

Abstract: Cobalt (2 %, 5 % and 10 %) doped cadmium selenide (CdSe) nanoparticles have been synthesized by soft chemical route. The XRD pattern shows the cubic structure of the sample. Crystallization temperature of the samples is calculated using differential scanning calorimeter. The average particle size of all the samples is found to be ∼ 25 nm. Field dependent (M-H) and temperature dependent (M-T) magnetization explains the presence of ferromagnetic components in the samples at room temperature and low temperature. In order to estimate the antiferromagnetic coupling among the doped TM atoms, an M-T measurement at 500 Oe has been carried out under zero field cooled (ZFC) and field cooled (FC) conditions and Curie-Weiss temperature θ of the samples has been estimated from 1/χ vs T plots.

Magnetic study of Fe-doped CdSe nanomaterials

Abstract: Nanoparticles of pure and iron (50 %) doped cadmium selenide (CdSe) have been synthesized by soft chemical route. EDAX analysis supports the inclusion of Fe into CdSe nanoparticles. The average particle size of pure and doped CdSe is found to be ∼50 nm from scanning electron microscopy (SEM). Magnetization of the samples are measured under the field cooled (FC) and zero field cooled (ZFC) modes in the temperature range from 5K to 300K applying a magnetic field of 500Oe. Field dependent magnetization (M-H) measurement indicates presence of room temperature (RT) paramagnetism and low temperature (5K) ferromagnetism of the sample.

The electrical modulus and other dielectric properties by the impedance spectroscopy of LaCrO3 and LaCr0.90Ir0.10O3 perovskites

Abstract: We have prepared LaCrO3 (LCO) and 10% Ir doped LCO samples by the solid state reaction method and studied the electrical modulus and the other dielectric properties of the samples by means of the impedance spectroscopy in the −100 °C to 100 °C range, with steps of 20 °C. It has been clearly observed that the dielectric properties change due to Ir doping. The absolute dielectric constant value of Ir doped LCO has decreased and this reduction was attributed to decreasing Cr6+ ions which may play a vital role in space charge polarization and charge hopping. A plateau region appeared in the temperature-dependent real electrical modulus M′ versus f curves of the pure LCO sample while almost no plateau region is visible in the Ir doped LCO sample. The temperature-dependent imaginary modulus M′′ versus f curves has two peaks at each temperature; one of the peaks is at low frequency and the other at the high frequency region, which shifts through higher frequency region with increasing temperature. This originates from free charge accumulation at the interface with the increase of the temperature. Furthermore, it has been seen that the Ir doped LCO sample has higher impedance and resistance values than the undoped LCO sample at the same frequency and temperature. This phenomenon was attributed to doped Ir ions behaving like a donor in LCO because LCO is a p-type compound. Moreover, the activation energy values of 0.224 eV and 0.208 eV for LCO and of 0.161 eV and 0.265 eV for the Ir doped LCO have been obtained from the slopes of the ρdc vs. (kT)−1 curves, respectively. Also the activation energies were calculated from the slopes of the fmax vs. (kT)−1 curves and the obtained results from low frequency region were in good agreement with ρdc vs. (kT)−1 ones.

Review on nanomaterials: Synthesis and applications

Abstract: The recent past in the technological development evidenced that evolution in Nanotechnology and nanoscience is the key factor. Nanotechnology is multidisciplinary science which deals with physics, chemistry, materials science and other engineering sciences. The applications of Nanotechnology are spreading in almost all the branches of science and technology. The present review article highlighted the types of nanoparticles and their synthesis methods, characterization techniques. There are many techniques and applications are reported in the last five years but here we strictly focused on the general synthetic approaches and applications of the nanomaterials which provide a general idea to the young researchers.

Impedance spectroscopy as a tool to monitor the adsorption and removal of nitrate ions from aqueous solution using zinc aluminum chloride anionic clay.

Abstract: In this study, Zn3AlCl ionic clay was used to investigate the adsorption mechanism of the nitrate ions in solutions containing nitrate ions at different contact time. The clay was synthesized by coprecipitation method at room temperature, and this sample was characterized by XRD, Fourier transform-infrared (FT-IR) and inductively coupled plasma (ICP). This sample was crystallized in a rhombohedral symmetry (Space group: R-3 m). Impedance spectroscopy was used as a tool to evaluate and monitor the adsorption process at different contact time 5; 10; 20; 30; 60 min and the clay alone. The impedance measurement was well analyzed and fitted with an equivalent circuit containing both (R//CPE) connected in series. Furthermore, the σac conductivity was also investigated as a function of frequency. It was analyzed and fitted using double power law: [Formula: see text] This study reveals the existence of two relaxation processes with different relaxation times, which could be attributed to the grain and grain boundaries, and exhibit high values of dielectric constant at low frequencies.

Light induced charge transport in La2NiMnO6 based Schottky diode

Abstract: La2NiMnO6 (LNMO) thin film is prepared on fluorine doped tin oxide (FTO) coated glass by chemical solution deposition technique. The room temperature crystal structure of LNMO is determined using X-ray diffraction and Raman spectra. The band gap (∼1.33 eV) obtained using UV–visible absorption spectrum of LNMO film is found to be very close to the Shockley-Queisser band gap (∼1.34 eV) for a single junction solar cell. A FTO/LNMO/Au type Schottky device is fabricated to explore the photo physical properties of LNMO thin film. A significant change in the resistance, barrier potential height, effective mobility, conductivity, charge carrier density and carrier diffusion length is observed when the experiment is performed under dark and white light illuminations. The thermionic emission theory is used to analyze the charge transport mechanism in the material.

Existence of nearest-neighbor and variable range hopping in Pr2ZnMnO6 oxygen-intercalated pseudocapacitor electrode

Abstract: The X-ray diffraction pattern and Raman spectrum authenticate the monoclinic P21/n structure of polycrystalline Pr2ZnMnO6 (PZM) synthesized by the solid-state reaction technique. The X-ray photoemission spectrum suggests the existence of oxygen vacancy in PZM, which plays a crucial role in electrical conduction as well as in electrochemical behavior. The existence of two different conduction mechanisms (such as nearest-neighbor hopping (NNH) and Mott's variable range hopping (MVRH)) is observed from the investigation of dc conductivity studies, dielectric relaxation, and impedance analysis of PZM. It is found that below 580 K, there is a transition from NNH to MVRH due to the decrease of activation energy. The constant phase element model is used to correlate the Nyquist plot and electric modulus of PZM. The bulk PZM electrode exhibits intercalated pseudocapacitive nature which offers an efficient specific capacitance of 69.14 F/g at a charge and discharge currents of 2 A/g in an aqueous solution of 1 M KOH. The charge storage mechanism of the PZM electrode has been analyzed and discussed.