68 research outputs found
Exploring magnetic and electronic properties in γ-Al<sub>2</sub>O<sub>3</sub>/SrTiO<sub>3</sub>
Analysis of the internal heat losses in a thermoelectric generator
A 3D thermoelectric numerical model is used to investigate different internal
heat loss mechanisms for a thermoelectric generator with bismuth telluride p-
and n-legs. The model considers all thermoelectric effects, temperature
dependent material parameters and simultaneous convective, conductive and
radiative heat losses, including surface to surface radiation. For radiative
heat losses it is shown that for the temperatures considered here, surface to
ambient radiation is a good approximation of the heat loss. For conductive heat
transfer the module efficiency is shown to be comparable to the case of
radiative losses. Finally, heat losses due to internal natural convection in
the module is shown to be negligible for the millimetre sized modules
considered here. The combined case of radiative and conductive heat transfer
resulted in the lowest efficiency. The optimized load resistance is found to
decrease for increased heat loss. The leg dimensions are varied for all heat
losses cases and it is shown that the ideal way to construct a TEG module with
minimal heat losses and maximum efficiency is to either use a good insulating
material between the legs or evacuate the module completely, and use small and
wide legs closely spaced.Comment: 11 pages, 9 figure
Charge transfer induced modulation doping of two-dimensional electron gas at complex oxide interfaces
Effect of Sr-doping of LaMnO3 spacer on modulation-doped two-dimensional electron gases at oxide interfaces
High-temperature thermoelectric properties of Na- and W-Doped Ca<sub>3</sub>Co<sub>4</sub>O<sub>9</sub> system
The detailed crystal structures and high temperature thermoelectric properties of polycrystalline Ca(3−2x)Na(2x)Co(4−x)W(x)O(9) (0 ≤ x ≤ 0.075) samples have been investigated. Powder X-ray diffraction data show that all samples are phase pure, with no detectable traces of impurity. The diffraction peaks shift to lower angle values with increase in doping (x), which is consistent with larger ionic radii of Na(+) and W(6+) ions. X-ray photoelectron spectroscopy data reveal that a mixture of Co(2+), Co(3+) and Co(4+) valence states are present in all samples. It has been observed that electrical resistivity (ρ), Seebeck coefficient (S) and thermal conductivity (κ) are all improved with dual doping of Na and W in Ca(3)Co(4)O(9) system. A maximum power factor (PF) of 2.71 × 10(−4) W m(−1) K(−2) has been obtained for x = 0.025 sample at 1000 K. The corresponding thermoelectric figure of merit (zT) for x = 0.025 sample is calculated to be 0.21 at 1000 K, which is ∼2.3 times higher than zT value of the undoped sample. These results suggest that Na and W dual doping is a promising approach for improving thermoelectric properties of Ca(3)Co(4)O(9) system
Extraordinary magnetometry -- a review on extraordinary magnetoresistance
Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance effect
occurring in hybrid devices consisting of a high-mobility material joined by a
metal. The change in resistance can exceed 107% at room temperature when a
magnetic field of 5 T is applied. Magnetic field sensors based on EMR hold the
potential formeasuring weak magnetic fields with an unprecedented sensitivity,
yet, to date this potential is largely unmet. In this work, we provide an
extensive review of the current state-of-the-art in EMR sensors with a focus on
the hybrid device geometries, the constituent material properties and
applications of EMR. We present a direct comparison of the best devices in
literature across magnetoresistance, sensitivity and noise equivalent field for
different materials and geometric designs. The compilation of studies collected
in this review illustrates the extremely rich possibilities for tuning the
magnetoresistive behavior varying the device geometry and material properties.
In addition, we aim to improve the understanding of the EMR effect and its
interplay with geometry and material properties. Finally, we discuss recent
trends in the field and future perspectives for EMR
Two-dimensional electron gases at a spinel/perovskite complex oxide heterointerface with electron mobilities exceeding 100,000 cm<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup>
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