Browsing by Author "Sakai, K."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Fabrication and thermoelectric characteristics of [(Bi,Pb)2Ba2O4±w]0.5CoO2 bulks with highly aligned grain structure(2008) Motohashi, T.; Nonaka, Y.; Sakai, K.; Karppinen, M.; Yamauchi, H.; Department of ChemistryHere, we report fabrication and thermoelectric characteristics of polycrystalline bulks with aligned grains of the misfit-layered cobalt oxides, [(Bi1−xPbx)2Ba2O4±w]0.5CoO2. High-quality precursor powder was prepared with a spray-drying technique. The precursor was then sintered under a uniaxial pressure to yield dense bulk samples consisting of highly aligned grains. The electrical conductivity of such samples was four times higher than that of conventionally sintered bulks. Accordingly, the thermoelectric characteristics of the grain-aligned specimens were enhanced.Item Fabrication and thermoelectric characteristics of [(Bi,Pb)[sub 2]Ba[sub 2]O[sub 4±w]][sub 0.5]CoO[sub 2] bulks with highly aligned grain structure(AIP Publishing, 2008) Motohashi, T.; Nonaka, Y.; Sakai, K.; Karppinen, Maarit; Yamauchi, H.; Kemian laitos; Department of Chemistry; Kemian tekniikan korkeakoulu; School of Chemical TechnologyHere, we report fabrication and thermoelectric characteristics of polycrystalline bulks with aligned grains of the misfit-layered cobalt oxides, [(Bi1−xPbx)2Ba2O4±w]0.5CoO2. High-quality precursor powder was prepared with a spray-drying technique. The precursor was then sintered under a uniaxial pressure to yield dense bulk samples consisting of highly aligned grains. The electrical conductivity of such samples was four times higher than that of conventionally sintered bulks. Accordingly, the thermoelectric characteristics of the grain-aligned specimens were enhanced.Item Pb-for-Bi substitution for enhancing thermoelectric characteristics of [(Bi,Pb)2Ba2O4±w]0.5CoO2(2006) Sakai, K.; Karppinen, Maarit; Chen, J.M.; Liu, Rushi; Sugihara, S.; Yamauchi, H.; Department of ChemistryWe report strongly enhanced thermoelectric characteristics for a misfit-layered oxide, [Bi2Ba2O4±ω]0.5CoO2, in a wide temperature range, as achieved through substituting up to 20% of Bi by Pb. The Pb substitution kept the thermal conductivity (κ) unchanged but decreased the electrical resistivity (ρ) and increased the Seebeck coefficient (S) simultaneously, such that a three-fold enhancement in the thermoelectric figure of merit, Z (≡S2/ρκ), was realized. At the same time x-ray absorption near-edge structure data indicated that the valence and spin states of Co are not affected by the Pb-for-Bi substitution.Item Pb-for-Bi substitution for enhancing thermoelectric characteristics of [(Bi,Pb)[sub 2]Ba[sub 2]O[sub 4±omega]][sub 0.5]CoO[sub 2](AIP Publishing, 2006) Sakai, K.; Karppinen, Maarit; Chen, J. M.; Liu, R. S.; Sugihara, S.; Yamauchi, H.; Kemian laitos; Department of Chemistry; Kemian tekniikan korkeakoulu; School of Chemical TechnologyWe report strongly enhanced thermoelectric characteristics for a misfit-layered oxide, [Bi2Ba2O4±omega]0.5CoO2, in a wide temperature range, as achieved through substituting up to 20% of Bi by Pb. The Pb substitution kept the thermal conductivity(κ) unchanged but decreased the electrical resistivity(ρ) and increased the Seebeck coefficient (S) simultaneously, such that a three-fold enhancement in the thermoelectric figure of merit, Z (≡S2/ρκ), was realized. At the same time x-rayabsorption near-edge structure data indicated that the valence and spin states of Co are not affected by the Pb-for-Bi substitution.