65 research outputs found
Enhanced magnetoresistance and Griffiths phase induced by Mo substitution in La0.7Ca0.15Sr0.15Mn1?xMoxO3 (0 <= x <= 0.05)
No full textTailoring of Seebeck coefficient with surface roughness effects in silicon sub-50-nm films
No full textThermoelectric properties of spark plasma sintered lead telluride nanocubes
No full textWe report a cost-effective, surfactant-free, and scalable synthesis technique for lead telluride (PbTe) nanocubes by a chemical precipitation method. The high-resolution transmission electron microscopy studies indicated the evolution of nucleation centers (spherical) into nanocubes with the addition of the Pb and Te atoms. The spark plasma sintered PbTe nanocubes exhibited an enhanced Seebeck coefficient, S > +400 mu V, higher than the reported values of the bulk PbTe over an extended temperature range of 300-425 K, and a moderate electrical conductivity, sigma similar to 8000 S/m at 300 K. A significant reduction in the lattice thermal conductivity was observed due to effective phonon scattering from the presence of numerous interfaces introduced by nanostructuring. The resulting figure-of-merit (ZT) similar to 0.45 at 300 K is higher than the reported values at this temperature in other PbTe nanostructures. Moreover, a moderate thermoelectric compatibility factor makes the PbTe nanocubes a potential candidate for green energy generation
Superiority of ion irradiation over annealing for enhancing the thermopower of PbTe thin films
No full textS.6-9Present study reveals that swift heavy ion (SHI) irradiation enhances thermoelectric properties and the annealing deteriorates thermoelectric performance of PbTe thin film. X-ray diffraction (XRD), Atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS) measurements are performed for phase formation, surface morphology and elemental composition of all the samples, respectively. Electrical conductivity (sigma) and thermo power (S) measurement of all the samples have also been measured using four probe method. The increase in thermo power (S) is about 40% upto high temperature (about 520 K) after irradiation whereas it decreases on annealing treatment. These findings are discussed on the basis of density of states enhancement or carrier scattering due to the point d efects after SHI irradiation.8
Effect of annealing temperature on the electrical characteristics of Platinum/4H-SiC Schottky barrier diodes
No full text
Size effect on magnetic ordering in Ce3Al1
No full text[[sponsorship]]物理研究所[[note]]已出版;[SCI];有審查制度;具代表
Development of pulsed magnetic field and study of magnetotransport properties of K-doped La1-xCax-yKyMnO3CMR materials
No full textTemperature-dependent magnetization, magnetoresistance and magneto-thermoelectric power of the K doped La1−xCax−yKyMnO3 type samples with x=0.3 and 0⩽y⩽0.15 has been studied. All the samples exhibit sharp metal–insulator transition (MIT) around Tp accompanied by a ferromagnetic (metallic) to paramagnetic (semiconducting) phase transition with a well-defined Curie temperature TC (almost equal to Tp). Doping of monovalent K in the divalent Ca site of La1−xCax−yKyMnO3 drives the system from a high resistivity regime with lower Tp to a lower resistivity regime with higher Tp. Systematic increase of Curie temperature with increase of K doing is observed from the magnetization measurement down to 5 K. Low temperature resistivity (ρ) and thermoelectric power (Seebeck coefficient, S) data well fit the relations ρ=ρ0+ρ2T2 and S=S0+S3/2T3/2+S4T4, respectively, signifying the importance of electron–magnon scattering process (ρ2T2 and S3/2T3/2 term). On the other hand, the high temperature (T>Tp upto 320 K) conductivity data satisfy the variable range hopping (VRH) model. For T>320 K small polaron hopping model is more appropriate than the VRH model. High temperature thermoelectric power (TEP) data also indicates the formation of thermally activated small polarons. Even with very small change of y, the density of states at the Fermi level N(EF) changes considerably. The magnetotransport properties have been measured under pulsed magnetic field of microsecond duration. The decay time of the magnetic pulse within the sample (ι) varies with field strength, which indicates that with change of magnetic field, ordering of the spin in the ferromagnetic regime changes
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