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Register a new userLow Temperature Thermoelectric Properties of Co- and Cr- doped CuAgSe
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High mobility phonon-glass semimetal $CuAgSe$ has shown promise in recent years as a potential low-temperature thermoelectric material. It exhibits reasonably strong thermoelectric performance as well as an extremely high carrier mobility, both of which are enhanced when the material is doped with Ni at the Cu sites. The exact mechanism by which these enhancements result; however, is unclear. In order to further investigate the effects of chemical substitution on the materials thermoelectric properties, we have prepared and performed various measurements on $CuAgSe$ samples doped with Co and Cr according to the following compositional formulas: $Cu_{1-x}Co_{x}AgSe$ $(x=0.02, 0.05, 0.10)$ and $Cu_{1-x}Cr_{x}AgSe$ $(x=0.02, 0.05)$. Measurements of temperature and magnetic field dependent thermal conductivity, electrical resistivity, and Seebeck coefficient will be discussed. Our results reveal a remarkable sensitivity of $CuAgSe$s thermoelectric properties to chemical doping in general as well as a particular sensitivity to specific dopants. This demonstrated tunability of $CuAgSe$s various properties furthers the case that high mobility phonon glass-semimetals are strong candidates for potential low temperature thermoelectric applications.
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We report here an experimental and theoretical study on the magnetoresistance properties of heavily phosphorous doped germanium on the metallic side of the metal-nonmetal transition. An anomalous regime, formed by negative values of the magnetoresistance, was observed by performing low-temperature measurements and explained within the generalized Drude model, due to the many-body effects. It reveals a key mechanism behind the magnetoresistance properties at low temperatures and, therefore, constitutes a path to its manipulation in such materials of great interest in fundamental physics and technological applications
The Seebeck coefficients, electrical resistivities, total thermal conductivities, and magnetization are reported for temperatures between 5 and 350 K for n-type Bi0.88Sb0.12 nano-composite alloys made by Ho-doping at the 0, 1 and 3% atomic levels. The alloys were prepared using a dc hot-pressing method, and are shown to be single phase for both Ho contents with grain sizes on the average of 900 nm. We find the parent compound has a maximum of ZT = 0.28 at 231 K, while doping 1% Ho increases the maximum ZT to 0.31 at 221 K and the 3% doped sample suppresses the maximum ZT = 0.24 at a temperature of 260 K.
The recent discovery of excellent thermoelectric properties and topological surface states in SnTe-based compounds has attracted extensive attention in various research areas. Indium doped SnTe is of particular interest because, depending on the doping level, it can either generate resonant states in the bulk valence band leading to enhanced thermoelectric properties, or induce superconductivity that coexists with topological states. Here we report on the vapor deposition of In-doped SnTe nanowires and the study of their surface oxidation and thermoelectric properties. The nanowire growth is assisted by Au catalysts, and their morphologies vary as a function of substrate position and temperature. Transmission electron microscopy characterization reveals the formation of amorphous surface in single crystalline nanowires. X-ray photoelectron spectroscopy studies suggest that the nanowire surface is composed of In2O3, SnO2, Te and TeO2 which can be readily removed by argon ion sputtering. Exposure of the cleaned nanowires to atmosphere yields rapid oxidation of the surface within only one minute. Characterizations of electrical conductivity {sigma}, thermopower S, and thermal conductivity k{appa} were performed on the same In-doped nanowire which shows suppressed {sigma} and k{appa} but enhanced S yielding an improved thermoelectric figure of merit ZT than the undoped SnTe.
We have measured thermoelectric properties of Ta2PdX6 (X=S, Se) around room temperature using single crystal samples. We find that the power factor of Ta2PdX6 is relatively high from middle-low to room temperatures, and notably Ta2PdSe6 shows the largest power factor among thermoelectric materials with an electrical conductivity of 10-2 {Omega}cm at 300 K. Ta2PdS6 will be a possible candidate for a Peltier cooling material if the lattice thermal conductivity is reduced by chemical substitution.
SrTiO$_3$ is a promising $n$-type oxide semiconductor for thermoelectric energy conversion. Epitaxial thin films of SrTiO$_3$ doped with both La and oxygen vacancies have been synthesized by pulsed laser deposition (PLD). The thermoelectric and galvanomagnetic properties of these films have been characterized at temperatures ranging from 300 K to 900 K and are typical of a doped semiconductor. Thermopower values of double-doped films are comparable to previous studies of La doped single crystals at similar carrier concentrations. The highest thermoelectric figure of merit ($ZT$) was measured to be 0.28 at 873 K at a carrier concentration of $2.5times10^{21}$ cm$^{-3}$.
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