E.C. Jones

Thermoelectric properties of CoSb3 and related alloys

Seebeck, electrical, and thermal conductivity data are reported on CoSb3, and doped and undoped alloys of Co1−x Ir x Sb3−y As y from 20 to 700 K. n‐type semiconductors were obtained by doping with Ni, Te, or Pd, and the hole concentration in p‐type samples was increased by substitution of Fe, Ru, Os, and Ge. An estimated maximum value for ZT of 0.6 (Z is the figure of merit) was found for a Te‐doped (n‐type) alloy at 700 K. For p‐type alloys, the maximum value of ZT was found to be 0.3 at 550 K. Electrical and thermal transport data also are reported for CoAs3, RhSb3, and IrSb3. Most of the samples investigated were polycrystalline, but a few measurements on CoSb3 single crystals also are discussed.

Thermoelectric properties of CoSb{sub 3} and related alloys

Seebeck, electrical, and thermal conductivity data are reported on CoSb3, and doped and undoped alloys of Co1−x Ir x Sb3−y As y from 20 to 700 K. n‐type semiconductors were obtained by doping with Ni, Te, or Pd, and the hole concentration in p‐type samples was increased by substitution of Fe, Ru, Os, and Ge. An estimated maximum value for ZT of 0.6 (Z is the figure of merit) was found for a Te‐doped (n‐type) alloy at 700 K. For p‐type alloys, the maximum value of ZT was found to be 0.3 at 550 K. Electrical and thermal transport data also are reported for CoAs3, RhSb3, and IrSb3. Most of the samples investigated were polycrystalline, but a few measurements on CoSb3 single crystals also are discussed.

Fluctuation conductivity of YBaCuO epitaxial thin films grown on various substrates

Abstract The fluctuation conductivity, in zero applied magnetic field, is analyzed for different high-quality c oriented epitaxial thin films of Y 1 Ba 2 Cu 3 O 7− x grown on various substrates; one ex-situ grown on single crystal LaAlO 3 and one in-situ grown on crystalline KTaO 3 , and one in-situ grown on polycrystalline YSZ. From the temperature dependence of the thermal fluctuation behavior, critical exponents are extracted, without fitting parameters, and the fluctuation dimensionality is deduced. Our findings are explicitly consistent with the thin-film structure of the sample and the conductivity behavior model proposed by Maki and Thompson. The first two epitaxial films show 2D dimensionality with a weak Maki-Thompson pair-breaking mechanism above T c , and a cross-over to a 3D dimensionality near T c . Moreover, the insensitivity to different substrate-induced lattice strains suggests that lattice strains do not alter the fluctuation behavior. The findings suggest a percolative mechanism in the polycrystalline film.

Anomalous transport and structural properties of Sr1-xCuO2-δ thin films

Abstract Transport and structural properties of Sr 1− x CuO 2−δ thin films grown by pulsed laser deposition support the contention that the tetragonal phase is capable of accommodating a significant density of alkaline-earth deficiencies up to x ≤0.3. Resistivity measurements indicate a significant change in the carrier density of the CuO 2 planes as Sr vacancies are introduced. In addition, an enigmatic anomaly in the resistivity at 185 K is observed for Sr 0.85 CuO 2−δ thin films. Magnetic measurements on these samples indicate that, although a significant drop in resistivity at 185 K is observed, it is not due to a superconducting transition. Hall measurements, as well as changes in the resistivity with film growth conditions, suggest that the majority carriers in these Sr 1− x CuO 2−δ thin films are electrons even with the Sr-vacancies present.

Defect formation and carrier doping in epitaxial films of the infinite layer compound

The correlation between defect formation and carrier doping in epitaxial films of the infinite layer compound SrCuO2 has been studied via molecular beam epitaxy controlled layer-by-layer growth experiments, chemically resolved scanning transmission electron microscopy,scanning tunneling microscopy, x-ray diffraction, electrical transport measurements, and post-growth oxidation-reduction annealing. Based on the complementary information provided by these experiments, it is concluded that the carrier doping is dominated by the formation of an electro-doped, Sr and O deficient matrix under mildly oxidizing growth conditions. Hole-doping is induced by extended defects containing excess Sr atoms and may lead to superconductivity after high- temperature oxidation.