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  • Digitale Medien  (11)
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  • Digitale Medien  (11)
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  • 1
    Digitale Medien
    Digitale Medien
    Low-temperature transport properties of the filled and unfilled IrSb3 skutterudite system (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8412-8418 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have measured the electrical resistivity, ρ, thermoelectric power, α, and thermal conductivity, κ, of the skutterudite material IrSb3 in a temperature range from 300 down to 4 K. It is found that the electrical resistivity and thermopower decrease monotonically as the temperature is reduced to 50–60 K. Below approximately 60 K the resistivity rises in a semiconducting manner. It appears the thermopower exhibits a large phonon drag peak at around 20 K and then falls towards zero. The thermal conductivity increases rapidly as the temperature is decreased with a maximum at around 20 K, corresponding to the peak in the thermopower. We will discuss these results and compare them to higher temperature data from G. A. Slack and V. G. Tsoukala [(IrSb3) J. Appl. Phys. 76, 1635 (1994)]. We have also measured some of the so-called "filled skutterudites,'' Ir4LaGe3Sb9, Ir4NdGe3Sb9 and Ir4SaGe3Sb9. The thermoelectric properties of these materials are considerably different than those of the unfilled sample. The thermopower is considerably lower and the resistivity is a factor of 2–4 times higher than the unfilled sample at room temperature. The thermal conductivity is markedly reduced by the filling, as much as a factor of 20 reduction for some of the systems. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362515
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  • 2
    Digitale Medien
    Digitale Medien
    Description of the parallel thermal conductance technique for the measurement of the thermal conductivity of small diameter samples (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1770-1774 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In order to measure the thermal conductivity of small needlelike samples (2.0×0.05×0.1 mm3) such as pentatellurides and single carbon fibers, we have developed a new technique called the parallel thermal conductance (PTC) technique. In the more typical steady state method that is used for measuring thermal conductivity, thermocouples are attached to the sample in order to measure the temperature gradient and a heater in order to supply this gradient. However, attaching thermocouples and heaters directly to small samples may be relatively difficult, and cause large heat losses and errors. Thus, the measurement of the thermal conductivity of small samples and thin films has been a formidable challenge, with only few successes, due, among other factors, to the heat loss. It is also difficult for the small samples to support the heaters and thermocouples without causing damage to the sample. In this paper we describe the recently developed PTC method providing measurements on standards as well as single carbon fibers, in addition to preliminary pentatelluride crystals measurements. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1347980
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  • 3
    Digitale Medien
    Digitale Medien
    Dynamic measurement access, a new technique for fast thermal conductivity measurement (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 3937-3939 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new technique called dynamic measurement access (DMA) is presented in this article which was developed for relatively easy, fast, and accurate thermal conductivity measurements. Utilizing a commercial cryocooler adapted for this experiment, the DMA technique allows the measurement of typically 400 data points in a temperature range between 300 and 10 K, during an elapsed time of approximately 90 min. This technique provides very good precision and requires a very simple experimental setup, which is described in this article. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1400148
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  • 4
    Digitale Medien
    Digitale Medien
    Transport and magnetism in La2/3Ca1/3(Mn1−xCox)O3 and La2/3Ca1/3(Mn1−xNix)O3 (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4974-4974 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: La2/3Ca1/3MnO3 is a strong double-exchange ferromagnet where the ratio of La3+–Ca2+ ions has been chosen to maximize its favorable magnetic and transport properties. The Mn ion is unique as an effective participant in the double-exchange process. It is of interest to add Ni or Co atoms substitutionally for Mn in the form of La2/3Ca1/3(Mn1−xCox)O3 and La2/3Ca1/3(Mn1−xNix)O3 in order to determine the relative importance of the double-exchange interaction as the Mn concentration is reduced. Powder x-ray diffraction reveals we can retain the original orthorhombic structure of La2/3Ca1/3MnO3 (with up to 50% Co or Ni substitution) by a series of anneals at 1300 °C followed by repeated grindings. We have investigated the magnetization, electrical conductivity, and thermopower of these mixed transition-metal perovskites. For La2/3Ca1/3(Mn1−xCox)O3, the magnetization decreases with added Co, but ferromagnetism is retained (at least up to 50% Co). Although metallic conductivity is still present at 10% Co concentration, these Co–Mn perovskites become insulating for x≥0.2. For La2/3Ca1/3(Mn1−xNix)O3, the metallic state is retained at least until x=0.5. The magnetic properties exhibit spin-glasslike behavior for x≥0.25. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364929
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  • 5
    Digitale Medien
    Digitale Medien
    Apparatus for the rapid measurement of electrical transport properties for both "needle-like" and bulk materials (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 3129-3131 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Described in this article is an apparatus in which thermopower and resistivity can be measured almost simultaneously from 10 to 300 K in a closed cycle refrigerator system. A distinction of this system is that the samples are mounted on integrated circuit (IC) chips for rapid introduction of the sample into the measurement apparatus. One advantage of this system is that the sample is mounted on the IC chip and then all the electrical contacts to the sample can be checked prior to insertion into the sample measurement apparatus. This system is applicable for measurement of either bulk samples (approximately 2×2×8 mm3) or "needle-like" samples (approximately 0.1×0.05×2–3 mm3). © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1380390
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  • 6
    Digitale Medien
    Digitale Medien
    Grain structure effects on the lattice thermal conductivity of Ti-based half-Heusler alloys (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 43-45 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Half-Heusler alloys with the general formula TiNiSn1−xSbx are currently being investigated for their potential as thermoelectric (TE) materials. A systematic investigation of the effect of Sb doping on the Sn site and Zr doping on the Ti site on the electrical and thermal transport of the TiNiSn system has been performed. Unexpectedly, lattice thermal conductivity κL appears to increase somewhat randomly with small amounts (x〈5%) of Sb doping. Subsequently, an investigation of grain structure in these Sb-doped materials has been found to correlate with the anomalous behavior of κL. Furthermore, effects of submicron grain sizes on κL in ball milled and shock compressed samples are also presented. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1488698
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of Sb doping on the thermoelectric properties of Ti-based half-Heusler compounds, TiNiSn1−xSbx (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2476-2478 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Half-Heusler alloys (MgAgAs type) with the general formula MNiSn where M is a group IV transition metal (Hf, Zr, or Ti) are currently under investigation for potential thermoelectric materials. These materials exhibit a high negative thermopower (−40 to −250 μV/K) and low electrical resistivity values (0.1–8 mΩ cm) both of which are necessary for a potential thermoelectric material. Results are presented in this letter regarding the effect of Sb doping on the Sn site (TiNiSn1−xSbx). The Sb doping leads to a relatively large power factor of (0.2–1.0) W/m K at room temperature for small concentrations of Sb. These values are comparable to that of Bi2Te3 alloys, which are the current state-of-the-art thermoelectric materials. The power factor is much larger at T(approximate)650 K where it is over 4 W/m K making these materials very attractive for potential power generation considerations. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1318237
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  • 8
    Digitale Medien
    Digitale Medien
    Investigation of the thermal conductivity of the mixed pentatellurides Hf1−xZrxTe5 (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2319-2321 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transition-metal pentatellurides (HfTe5 and ZrTe5) exhibit a promising power factor (electronic properties) for possible use as a thermoelectric material. For complete characterization of these crystals, thermal conductivity measurements are necessary. In this letter, we report measurements of the thermal conductivity for this group of materials using the parallel thermal conductance technique which is well adapted for needle-like samples. Thermal conductivity is presented as a function of temperature and composition of the pentatelluride solid solution HfxZr1−xTe5 with 0≤x≤1 in which the magnitude of the room temperature thermal conductivity varies from 5 to 8 W/(m K). Dependence on the cross-sectional area and possible size effects (or sample quality) is also presented and discussed. These results also indicate the importance of sample quality on the low-temperature thermal conductance maximum λmax. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1316065
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  • 9
    Digitale Medien
    Digitale Medien
    Effect of Ti substitution on the thermoelectric properties of the pentatelluride materials M1−xTixTe5 (M=Hf, Zr) (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2056-2058 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thermoelectric properties (resistivity and thermopower) of single crystals of the low dimensional pentatelluride materials, HfTe5 and ZrTe5, have been measured as a function of temperature from 10 K〈T〈320 K. The effect of small amounts of Ti substitutional doping (M1−xTixTe5, where M=Hf, Zr) on the thermoelectric properties is reported here. A resistive transition occurs in the pentatellurides, as evidenced by a peak in the resistivity, TP(approximate)80 K for HfTe5 and TP(approximate)145 K for ZrTe5. Both parent materials exhibit a large positive (p-type) thermopower near room temperature which undergoes a change to negative (n-type) below the peak temperature. The thermal conductivity is relatively low ((approximate)5 W/m K) for the MTe5 materials. The Ti substitution affects the electronic properties strongly, producing a substantial shift in the peak temperature while the large values of thermopower remain essentially unaffected. These results warrant further investigation of these materials as candidates for low temperature thermoelectric applications. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.121406
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  • 10
    Digitale Medien
    Digitale Medien
    Thermal and electrical transport properties of the single-phase quasicrystalline material: Al70.8Pd20.9Mn8.3 (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1854-1856 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The electrical and thermal transport properties of a single-phase quasicrystalline material of composition Al70.8Pd20.9Mn8.3 have been measured as a function of temperature (T) over a range of 10 K〈T〈320 K. The following room-temperature values were found: electrical conductivity [640 (Ω cm)−1], Seebeck coefficient (85 μV/K), and thermal conductivity (1.6 W/m K). As the temperature was decreased from room temperature, the electrical conductivity decreased undergoing a minimum at T(approximate)50 K after which it increased slightly and the Seebeck coefficient decreased monotonically. The thermal conductivity decreased with temperature and exhibited a broad plateau region between 50 K〈T〈150 K. This class of materials is being investigated for potential thermoelectric applications. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.124850
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