Studies on La2-xPrxCayBa2Cu4+yOz (0.1 < x < 0.5) type mixed oxide superconductors

The La2-xPrxCayBa2Cu4+yOz (LaPrCaBCO) mixed oxides have been studied for their structural and superconducting properties using X-ray diffraction (XRD), d. c. resistivity, d. c. susceptibility and iodometric double titration. All the LaPrCaBCO samples for x = 0.1 - 0.5, exhibit tetragonal crystalline structure with P 4/mmm space group as determined by Rietveld analysis of the X-ray diffraction data. With increasing x, enhancement in Tc is observed, which is quite interesting for Pr substituted high Tc oxides. Maximum Tc ~ 58 K has been observed for x = 0.5(La-2125 stoichiometry). The results of structural studies and superconducting property measurements are presented in light of increase in Tc in LaPrCaBCO system with increasing Pr concentration.Comment: 6 pages including 5 figures and 1 tabl

Transport Properties of Bismuth Telluride Compound Prepared by Mechanical Alloying

We have synthesized bismuth telluride compound using mechanical alloying and hot press sintering method. The phase formation, crystal structure was evaluated by X-ray diffraction and Raman spectroscopy. The scanning electron microscopy images indicated sub-micron sized grains. We observed low value of thermal conductivity 0.39 W/mK at room temperature as a result of grain size reduction by increasing deformation. The performance of the samples can be improved by reducing the grain size, which increases the grain boundary scattering. REFERENCE

Two-Dimensional Halide Perovskite Materials Featuring 2‑(Methylthio)ethylamine Organic Spacers for Efficient Solar and Thermal Energy Harvesting

Two-dimensional (2D) halide-based hybrid perovskites are recognized as emerging materials for solar cells and thermoelectric applications. Here, we report on the electronic, optical, and thermoelectric properties of the 2-(methylthio)ethylamine (MTEA)-based 2D perovskites (MTEA)2PbI4 and (MTEA)2(MA)Pb2I7 using density functional theory calculations. The Rashba-splitting strength is observed to lie between 0.41 and 0.65 eV Å at four positions of the band structure of (MTEA)2(MA)Pb2I7. The strong sulfur–sulfur interaction between MTEA spacers results in a noticeable shift in the onset of the absorption spectrum. For (MTEA)2(MA)Pb2I7, a larger theoretical limit in the power conversion efficiency (29%) is calculated compared to (MTEA)2PbI4, which can be attributed to the absorption coefficient difference in both structures. The considered structures show very small effective electron masses, which results in an exceptionally high electron carrier mobility. The calculations yield an extremely large thermoelectric power factor of 42.3 mW/mK2 for (MTEA)2(MA)Pb2I7 at 300 K, which is even higher than that of 3D and 2D perovskites reported so far. The present work suggests that the (MTEA)-based 2D perovskites are promising candidates for application in solar- and thermal-energy harvesting

Colossal electroresistance in Sm(0.55)Sr(0.45)MnO(3)

We report a colossal resistance drop around insulator-metal transition temperature (T(MI)) in Sm(0.55)Sr(0.45)MnO(3) induced by direct current. Polycrystalline samples of Sm(0.55)Sr(0.45)MnO(3) were synthesized through solid state reaction method. They have been investigated by X-ray diffraction for phase evaluation, scanning electron microscopy for grain morphology and dc resistivity measurement techniques for resistivity-temperature behavior. The resistivity-temperature behavior has been measured with different biasing currents (1 mA, 2.5 mA, 5 mA, 10 mA and 50 mA). With increasing biasing current, the resistivity of the samples decreased drastically. The change in the resistivity of the samples for bias currents 1 mA and 50 mA at T(MI) was found to be similar to 2560%. This phenomenon of electroresistance is discussed in view of strong interaction between carrier spins and localized spins in Mn ions and percolative mechanism of phase-separation. (c) 2010 Elsevier B.V. All rights reserved

Room-temperature H2S gas sensing at ppb level by single crystal In2O3 whiskers

10.1016/j.snb.2008.03.003Sensors and Actuators B: Chemical1332456-46

Synthesis & Tailoring the Thermal Conductivity of Sr Doped Bi2Se3 Thermoelectric Material

We have investigated the thermal transport properties of SrxBi(2)-xSe(3) (x=0, 0.05, 0.2). The samples were synthesized by melt route method followed by vacuum hot press. The structural and morphological information of sample has been retrieved using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal transport measurement were performed in the temperature range of 300-550 K. It is found that with increasing Sr content the total thermal conductivity of the material decreases which is attributed to the enhance phonon scattering due to natural grown layered structure and defect induced by Sr doping

Preparation and Characterization of HgO and AgO Added La2CaBa2Cu5Oz Superconductors

We have prepared a series of La2CaBa2Cu5O (z) (La2125) compounds by the standard solid-state reaction method. The oxygen stoichiometry in this R-123 type compound has been homogenized by two different methods. The first method is heating the sample in flowing oxygen at 500 A degrees C for 6 hours and then slowly cooling to room temperature. The second method is to provide internal oxygen while sintering the sample by adding HgO or AgO. The addition of HgO or AgO in preparing oxide superconductors is advantageous when preparing them in bulk quantities, as HgO or AgO provide internal oxygen which is a much essential ingredient of the structure of oxide superconductors. Such a method of synthesis eliminates the need of additional oxygen annealing, thus enabling the synthesis in huge quantities at once. The composites referred to as La2125+xHgO and La2125+xAgO respectively, have been characterized by XRD, SEM, resistivity and magnetic measurements for their structural and superconducting properties. We compare the properties of oxygen-annealed and HgO/AgO added compounds and discuss the results in the light of applicability of such method in synthesizing bulk quantities of high-T (c) oxide superconductors

Synthesis & Tailoring the Thermal Conductivity of Sr Doped Bi2Se3 Thermoelectric Material

We have investigated the thermal transport properties of SrxBi(2)-xSe(3) (x=0, 0.05, 0.2). The samples were synthesized by melt route method followed by vacuum hot press. The structural and morphological information of sample has been retrieved using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal transport measurement were performed in the temperature range of 300-550 K. It is found that with increasing Sr content the total thermal conductivity of the material decreases which is attributed to the enhance phonon scattering due to natural grown layered structure and defect induced by Sr doping