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Author: Schierning, G. ×

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    Thermoelectric properties of silicon and recycled silicon sawing waste
    (Peking : Chinese Ceramic Society, 2019) He, R.; Heyn, W.; Thiel, F.; Pérez, N.; Damm, C.; Pohl, D.; Rellinghaus, B.; Reimann, C.; Beier, M.; Friedrich, J.; Zhu, H.; Ren, Z.; Nielsch, K.; Schierning, G.
    Large-scale-applicable thermoelectric materials should be both self-sustaining, in order to survive long-term duty cycles, and nonpolluting. Among all classes of known thermoelectric materials, these criteria reduce the available candidate pool, leaving silicon as one of the remaining options. Here we first review the thermoelectric properties of various silicon-related materials with respect to their morphologies and microstructures. We then report the thermoelectric properties of silicon sawing wastes recycled from silicon wafer manufacturing. We obtain a high power factor of ∼32 μW cm−1 K−2 at 1273 K with 6% phosphorus substitution in the Si crystal, a value comparable to that of phosphorus-doped silicon-germanium alloys. Our work suggests the large-scale thermoelectric applicability of recycled silicon that would otherwise contribute to the millions of tons of industrial waste produced by the semiconductor industry.
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    Fluctuation-dissipation in thermoelectric sensors
    (Les-Ulis : EDP Science, 2023) Tran, N.A.M.; Dutt, A.S.; Pulumati, N.B.; Reith, H.; Hu, A.; Dumont, A.; Nielsch, K.; Tremblay, A.-M.S.; Schierning, G.; Reulet, B.; Szkopek, T.
    Thermoelectric materials exhibit correlated transport of charge and heat. The Johnson-Nyquist noise formula 4k B T R for the spectral density of voltage fluctuations accounts for fluctuations associated solely with Ohmic dissipation. Applying the fluctuation-dissipation theorem, we generalize the Johnson-Nyquist formula for thermoelectrics, finding an enhanced voltage fluctuation spectral density 4k B T R(1 + Z D T) at frequencies below a thermal cut-off frequency f T, where Z D T is the dimensionless thermoelectric device figure of merit. The origin of the enhancement in voltage noise is thermoelectric coupling of temperature fluctuations. We use a wideband , integrated thermoelectric micro-device to experimentally confirm our findings. Measuring the Z D T enhanced voltage noise, we experimentally resolve temperature fluctuations with a root mean square amplitude of at a mean temperature of 295 K. We find that thermoelectric devices can be used for thermometry with sufficient resolution to measure the fundamental temperature fluctuations described by the fluctuation-dissipation theorem.
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    Entropy of conduction electrons from transport experiments
    (Basel : MDPI AG, 2020) Pérez, N.; Wolf, C.; Kunzmann, A.; Freudenberger, J.; Krautz, M.; Weise, B.; Nielsch, K.; Schierning, G.
    The entropy of conduction electrons was evaluated utilizing the thermodynamic definition of the Seebeck coefficient as a tool. This analysis was applied to two dierent kinds of scientific questions that can-if at all-be only partially addressed by other methods. These are the field-dependence of meta-magnetic phase transitions and the electronic structure in strongly disordered materials, such as alloys. We showed that the electronic entropy change in meta-magnetic transitions is not constant with the applied magnetic field, as is usually assumed. Furthermore, we traced the evolution of the electronic entropy with respect to the chemical composition of an alloy series. Insights about the strength and kind of interactions appearing in the exemplary materials can be identified in the experiments.