Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Michitaka Ohtaki Last modified date:2019.08.05

Professor / Molecular and Materials Physical Chemistry / Department of Advanced Materials Science and Engineering / Faculty of Engineering Sciences


Papers
1. Koichiro Suekuni, Hidetomo Usui, Siying Qiao, Katsuaki Hashikuni, Tatsuya Hirano, Hirotaka Nishiate, Chul Ho Lee, Kazuhiko Kuroki, Kosuke Watanabe, Michitaka Ohtaki, Electronic structure and thermoelectric properties of Sn
1.2- x
Nb
x
Ti
0.8
S
3
with a quasi-one-dimensional structure, Journal of Applied Physics, 10.1063/1.5093183, 125, 17, 2019.05, We report the electronic structure and thermoelectric properties of a tin titanium trisulfide, Sn
1.2
Ti
0.8
S
3
. The crystal structure is composed of infinite "ribbons" of double edge-sharing (Sn
4+
/Ti
4+
)S
6
octahedra capped by Sn
2+
. First-principles calculations predict a nearly unidirectional transport of electrons along the ribbon axis for a single crystal and the existence of lone-pair electrons on Sn
2+
. Experiments on polycrystalline pressed samples demonstrate that Sn
1.2
Ti
0.8
S
3
exhibits semiconducting temperature dependence of electrical resistivity and a large negative Seebeck coefficient at room temperature. Substitution of Nb
5+
for Sn
4+
at the octahedral sites increases the electron carrier concentration, leading to an enhancement of the thermoelectric power factor. Anisotropy in the electronic properties is weak because of a weak orientation of the ribbon axis of crystallites in the pressed sample. The lattice thermal conductivity is less than 1 W K
-1
m
-1
for the pristine and substituted samples, which is attributed to weak bonding between the ribbons via the lone-pair electrons of Sn
2+
and to random occupation of Sn
4+
, Ti
4+
, and Nb
5+
at the octahedral sites..
2. Katsuaki Hashikuni, Koichiro Suekuni, Hidetomo Usui, Raju Chetty, Michihiro Ohta, Kazuhiko Kuroki, Toshiro Takabatake, Kosuke Watanabe, Michitaka Ohtaki, Thermoelectric Properties and Electronic Structures of CuTi
2
S
4
Thiospinel and Its Derivatives
Structural Design for Spinel-Related Thermoelectric Materials, Inorganic Chemistry, 10.1021/acs.inorgchem.8b02955, 58, 2, 1425-1432, 2019.01, We report the preparations, thermoelectric and magnetic properties, and electronic structures of Cu-Ti-S systems, namely, cubic thiospinel c-Cu
1-x
Ti
2
S
4
(x ≤ 0.375), a derivative cubic and Ti-rich phase c-Cu
1-x
Ti
2.25
S
4
(x = 0.5, 0.625), and a rhombohedral phase r-CuTi
2
S
4
. All samples have the target compositions except for r-CuTi
2
S
4
, whose actual composition is Cu
1.14
Ti
1.80
S
4
. All of the phases have n-type metallic character and exhibit Pauli paramagnetism, as proven by experiments and first-principles calculations. The Cu and Ti deficiencies in c-Cu
1-x
Ti
2
S
4
and r-CuTi
2
S
4
, respectively, decrease the electron-carrier concentration, whereas the "excess" of Ti ions in c-Cu
1-x
Ti
2.25
S
4
largely increases it. For r-CuTi
2
S
4
, the reduced carrier concentration increases the electrical resistivity and Seebeck coefficient, leading to the highest thermoelectric power factor of 0.5 mW K
-2
m
-1
at 670 K. For all of the Cu-Ti-S phases, the thermal conductivity at 670 K is 3.5-5 W K
-1
m
-1
, where the lattice part of the conductivity is as low as 1 W K
-1
m
-1
at 670 K. As a result, r-CuTi
2
S
4
shows the highest dimensionless thermoelectric figure of merit ZT of 0.2. The present systematic study on the Cu-Ti-S systems provides insights into the structural design of thermoelectric materials based on Cu-M-S (M = transition-metal elements)..
3. Koichiro Suekuni, Yuta Shimizu, Eiji Nishibori, Hidetaka Kasai, Hikaru Saito, Daichi Yoshimoto, Katsuaki Hashikuni, Yohan Bouyrie, Raju Chetty, Michihiro Ohta, Emmanuel Guilmeau, Toshiro Takabatake, Kosuke Watanabe, Michitaka Ohtaki, Atomic-scale phonon scatterers in thermoelectric colusites with a tetrahedral framework structure, Journal of Materials Chemistry A, 10.1039/c8ta08248k, 7, 1, 228-235, 2019.01, Copper-based chalcogenides with tetrahedral framework structures have been attracting increasing attention as environmentally friendly thermoelectric materials. A representative group of such thermoelectric chalcogenides is the Cu 26 A 2 M 6 S 32 (A = V, Nb, Ta; M = Ge, Sn) family of colusites, which exhibit low electrical resistivity, a large Seebeck coefficient, and low thermal conductivity; these properties are necessary for efficient thermal-to-electronic energy conversion. Here, we show the impact of crystal structure on the lattice thermal conductivity of colusite with A = Nb, M = Sn. The crystal structure can be modified by controlling the cationic compositions and the deficiency in the sulfur content as Cu 26-x Nb 2 Sn 6+x S 32-δ . The Cu/Sn ratio is found to be the key parameter for exsolution into distinct phases with ordered and disordered arrangements of cations. For the ordered-structure phase, sulfur sublimation induces atomic-scale defects/disordered states including interstitial defects, anti-site defects, and site splitting, which function as strong phonon scatterers, and the lowest lattice thermal conductivity of ∼0.5 W K -1 m -1 is achieved for the modified ordered structure. This finding provides a simple approach to modifying the crystal structure of thermoelectric chalcogenides via the loss of anions to reduce their lattice thermal conductivity..
4. Yulia Eka Putri, Suhana Mohd Said, Refinel Refinel, Michitaka Ohtaki, Syskri Syukri , Low Thermal Conductivity of RE-Doped SrO(SrTiO3)1 Ruddlesden Popper Phase Bulk Materials Prepared by Molten Salt Method, Electronic Materials Letters, 10.1007/s13391-018-0062-x, 1-7, 2018.04.
5. Katsuaki Hashikuni, Koichiro Suekuni, Kosuke Watanabe, Yohan Bouyrie, Michihiro Ohta, Michitaka Ohtaki, ToshiroTakabatake, Carrier Concentration Tuning in Thermoelectric Thiospinel Cu2CoTi3S8 by Oxidative Extraction of Copper, Journal of Solid State Chemistry, 10.1016/j.jssc.2017.12.031, 259, 5-10, 2018.03.
6. Takuya Kagawa and Michitaka Ohtaki, Synthesis and Thermoelectric Properties of Layered Oxyselenides and Oxyphosphides, Proceedings of the 18th Cross Straits Symposium on Energy and Environmental Science and Technology, 18, 269-270, 2016.12.
7. Shinji Hirata and Michitaka Ohtaki, Synthesis and Thermoelectric Properties of Nanoporous Oxide Composites Containing Metal Nanoparticles, Proceedings of the 18th Cross Straits Symposium on Energy and Environmental Science and Technology, 18, 35-36, 2016.12.
8. Kohei Mizuta, Michitaka Ohtaki, Crystal Structure and Thermoelectric Properties of β-Pyrochlore-Type Alkali Iron Tungsten Oxides with Cage-Like Structure, Journal of Electronic Materials, 10.1007/s11664-015-4179-5, 45, 3, 1695-1699, 2016.03.
9. Yoshinao Kai and Michitaka Ohtaki, Thermoelectric Properties of Ferroelectric Oxides Reduced by Hydrogen, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 121-122, 2015.12.
10. Shin-ichi Hayano and Michitaka Ohtaki, Synthesis of Nanosized Layered Compounds with Molecular Assembly Template and Characteristics Changes with Post-treatment, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 117-118, 2015.12.
11. Yosuke Araki and Michitaka Ohtaki, Synthesis of NaFeO2-xPx by P-doping of Layered Oxide NaFeO2, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 115-116, 2015.12.
12. Fumihiro Ishibashi and Michitaka Ohtaki, Synthesis of Low-dimensional Nanomaterials in Mesoporous Silica, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 113-114, 2015.12.
13. Shinji Hirata and Michitaka Ohtaki, Synthesis and Thermoelectrics Properties of Nanoporous Oxide Formed by Selective Leaching of Metal Nanoparticles, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 111-112, 2015.12.
14. Kei Watanabe and Michitaka Ohtaki, Switching the Thermal Conductivity by Phase Transitions in Metal Oxides, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 105-106, 2015.12.
15. Toshifumi Ogawa and Michitaka Ohtaki, Effects of microstructure on thermoelectric properties of dually doped ZnO, Proceedings of the 17th Cross Straits Symposium on Energy and Environmental Science and Technology, 17, 97-98, 2015.12.
16. Taiga Kuragaki, Michitaka Ohtaki, Performance Stability of ZnO-based Oxide Thermoelectric Materials at High Temperature, Proceedings of the 16th Cross Straits Symposium on Energy and Environmental Science and Technology, 181-182, 2014.11.
17. Kohei Mizuta, Michitaka Ohtaki, Cage-like Structure Oxides AAl0.33Te1.67O6 with Unconventional Phonon Scattering, Proceedings of the 16th Cross Straits Symposium on Energy and Environmental Science and Technology, 175-176, 2014.11.
18. Michitaka Ohtaki, Oxide Thermoelectric Materials for Power Generation from Mid-to-High Temperature Unused Heat Energy, Proceedings of the 16th Cross Straits Symposium on Energy and Environmental Science and Technology, 29-32, 2014.11.
19. Li Han, Ngo Van Nong, Wei Zhan, Le Thanh Hung, Tim Holgate, Kazunari Tashiro, Michitaka Ohtaki, Nini Pryds, Søren Linderoth, Effects of morphology on the thermoelectric properties of Al-doped ZnO, RSC Advances, 4, 24, 12353-12361, 2014.02.
20. Tohru Sugahara, Michitaka Ohtaki, Katsuaki Suganuma, La doped effects on structure and thermoelectric properties of Sr2MnMoO6 double-perovskite oxides, Journal of Asian Ceramic Societies, 1, 3, 282-288, 2013.09.
21. Michitaka Ohtaki, So Miyaishi, Extremely Low Thermal Conductivity in Oxides with Cage-like Crystal Structure
, Journal of Electronic Materials, 10.1007/s11664-012-2382-1, 42, 2013.06.
22. Nguyen Viet Long, Michitaka Ohtaki, Masayoshi Yuasa, Satoshi Yoshida, Taiga Kuragaki, Gao Minh Thi, Masayuki Nogami, Synthesis and Self-Assembly of Gold Nanoparticles by Chemically Modified Polyol Methods under Experimental Control, Journal of Nanomaterials, 2013, 793125, 2013.04.
23. Li Han, Ngo Van Nong, Le Thanh Hung, Nini Pryds, Michitaka Ohtaki, Søren Linderoth, The Influence of α- and γ-Al2O3 Phases on the Thermoelectric Properties of Al-doped ZnO
, Journal of Alloys and Compounds, 555, 291-296, 2013.04.
24. Nguyen Viet Long, Masayuki Nogami, Cao Minh Thi, Michitaka Ohtaki, Experimental Evidences of Crystal Nucleation and Growth of Platinum Nanoparticles with Most Characteristic Roughness Heteromorphologies and Nanostructures from Homogeneous Solution, Journal of Advanced Microscopy Research, 7, 1-20, 2012.09.
25. Nguyen Viet Long, Michitaka Ohtaki, Takashi Matsubara, Cao Minh Thi, Masayuki Nogami, New Experimental Evidences of Pt-Pd Bimetallic Nanoparticles with Core-Shell Configuration and Highly Fine-ordered Nanostructures by High-Resolution Electron Transmission Microscopy, The Journal of Physical Chemistry C, 116, 22, 12265-12274, 2012.06, In our facile synthesis method, poly(vinylpyrrolidone) protected Pt and Pt-Pd bimetallic nanoparticles with controllable polyhedral core-shell morphologies are precisely synthesized by the reduction of Pt and Pd precursors at a certain temperature in ethylene glycol and silver nitrate as structure-controlling agent. The Pt nanoparticles exhibited well-shaped polyhedral morphology with highly fine and specific nanostructures in the nanosized range of 20 nm. Important evidences of core-shell configurations of the Pt-Pd core-shell nanoparticles were clearly characterized by high-resolution transmission electron microscopy (HRTEM) measurements. The results of HRTEM images showed that the core-shell Pt-Pd nanoparticles in the nanosized range of 25 nm with polyhedral morphology were synthesized with the thin Pd shells of the nanosized range of about 3 nm in thickness as the atomic Pd layers grown on the as-prepared Pt cores in the nanosized range. The very interesting characterization of surface structure of Pt nanostructures and Pt-Pd core-shell nanostructures with surface defects were observed. The high-resolution TEM images of Pt-Pd bimetallic nanoparticles showed that the Frank-van-der Merwe and Stranski-Krastanov growth modes coexist in the nucleation and growth of the Pd shells on the as-prepared Pt cores. The lattice-fringe spacing was estimated as around 0.240 nm, which is assigned exactly to the lattice-fringe spacing of the {111} planes of the Pd metal shell observed. It is predicted that the FM growth becomes a more favorable growth mode compared to the SK growth in the formation of the very thin Pd shells of Pt-Pd core-shell nanoparticles. The experimental evidences of the deformations of lattice fringes and lattice-fringe patterns were found in polyhedral Pt nanoparticles as well as polyhedral Pt-Pd core-shell nanoparticles. The interesting re-nucleation and re-crystallization at their connections or their attachments of the as-prepared nanoparticles are found in a good lattice match. In addition, our novel ideas of the largest surface-area superlattices and suitable utilization of such large surface areas are proposed for next generations of various fuel cells with low cost. Finally, the products of as-prepared Pt-Pd core-shell nanoparticles can potentially utilized as highly efficient catalysts in the realization of polymer electrolyte membrane cell (PEMFC) and direct methanol fuel cell (DMFC) using the very low Pt loading with better cost effective design..
26. Nguyen Viet Long, Cao Minh Thi, Masayuki Nogami, Michitaka Ohtaki, Novel Issues of Morphology, Size, and Structure of Pt Nanoparticles in Chemical Engineering: Surface Attachment, Aggregation or Agglomeration, Assembly, and Structural Changes, New Journal of Chemistry, 10.1039/C2NJ40027H, 2012.06.
27. Tohru Sugahara, Teppei Araki, Michitaka Ohtaki, Katsuaki Suganuma, Structure and Thermoelectric Properties of Double-perovskite Oxides: Sr2-xKxFeMoO6, Journal of the Ceramic Society of Japan, 120, 6, 211-216, 2012.06.
28. Tohru Sugahara, Ngo Van Nong, Michitaka Ohtaki, Structure and Thermoelectric Properties of Ca2-xSrxFeMoO6 (0 ≤ x ≤ 0.3) Double-perovskite Oxides, Materials Chemistry and Physics, 133, 2-3, 630-634, 2012.04.
29. Nguyen Viet Long, Nguyen Duc Chien, Tomokatsu Hayakawa, Takashi Matsubara, Michitaka Ohtaki, Masayuki Nogami, Sharp Cubic and Octahedral Morphologies of Poly(vinylpyrrolidone)-stabilised Platinum Nanoparticles by Polyol Method in Ethylene Glycol: Their Nucleation, Growth and Formation Mechanisms, Journal of Experimental Nanoscience, 7, 2, 133-149, 2012.03.
30. Michitaka Ohtaki, Kazuhiko Araki, Thermoelectric Properties and Thermopower Enhancement of Al-doped ZnO with Nanosized Pore Structure, Journal of the Ceramic Society of Japan, 119, 11, 813-816, 2011.11.
31. Nguyen Viet Long, Michitaka Ohtaki, Tong Duy Hien, Jalem Randy, Masayuki Nogami, Synthesis and Characterization of Polyhedral and Quasi-sphere Non-polyhedral Pt Nanoparticles: Effects of Their Various Surface Morphologies and Sizes on Electrocatalytic Activity for Fuel Cell Applications, Journal of Nanoparticle Research, 13, 10, 5177-5191, 2011.10.
32. Nguyen Viet Long, Michitaka Ohtaki, Tong Duy Hien, Jalem Randy, Masayuki Nogami, A Comparative Study of Pt and Pt-Pd Core-shell Nanocatalysts, Electrochimica Acta, 56, 25, 9133-9143, 2011.10.
33. Nguyen Viet Long, Michitaka Ohtaki, Masayuki Nogami, Tong Duy Hien, Effects of Heat Treatment and Poly(vinylpyrrolidone) (PVP) Polymer on Electrocatalytic Activity of Polyhedral Pt Nanoparticles towards their Methanol Oxidation, Colloid and Polymer Science, 289, 12, 1373-1386, 2011.08.
34. Tohru Sugahara, Michitaka Ohtaki, Structural and Semiconductor-to-metal Transitions of Double-perovskite Cobalt Oxide Sr2-xLaxCoTiO6-d with Enhanced Thermoelectric Capability, Applied Physics Letters, 99, 6, 062107, 2011.08.
35. Nguyen Viet Long, Michitaka Ohtaki, Masaya Uchida, Randy Jalem, Hirohito Hirata, Nguyen Duc Chien, Masayuki Nogami, Synthesis and Characterization of Polyhedral Pt Nanoparticles: Their Catalytic Property, Surface Attachments, Self-aggregation and Assembly, Journal of Colloid and Interface Science, 359, 2, 339-350, 2011.07.
36. Nguyen Viet Long, Masaya Uchida, Jalem Randy, Hirohito Hirata, Nguyen Duc Chien, Michitaka Ohtaki, Masayuki Nogami, Synthesis and Characterization of Pt-Pd Alloy and Core-shell Bimetallic Nanoparticles for Direct Methanol Fuel Cells (DMFCs): Enhanced Electrocatalytic Properties of Well-shaped Core-shell morphologies and Nanostructures, International Journal of Hydrogen Energy, 36, 14, 8478-8491, 2011.07.
37. Nguyen Viet Long, Tong Dui Hien, Toru Asaka, Michitaka Ohtaki, Masayuki Nogami, Synthesis and Characterization of Pt-Pd Nanoparticles with Core-shell morphology: Nucleation and Overgrowth of the Pd Shells on the as-prepared and Defined Pt Seeds, Journal of Alloys and Compounds, 509, 29, 7702-7709, 2011.07.
38. Ngo Van Nong, Nini Pryds, Soren Linderoth, Michitaka Ohtaki, Enhancement of the Thermoelectric Performance of p-Type Layered Oxide Ca3Co4O9+d Through Heavy Doping and Metallic Nanoinclusions, Advanced Materials, 23, 21, 2484-2490, 2011.06.
39. Ngo Van Nong, Syun-ichi. Yanagiya, Sonne Monica, Nini Pryds, Michitaka Ohtaki, High-Temperature Thermoelectric and Microstructural Characteristics of Cobalt-Based Oxides with Ga Substituted on the Co-Site, Journal of Electronic Materials, 40, 5, 716-722, 2011.05.
40. Nguyen V. Long, Michitaka Ohtaki, Masayuki Nogami, Control of Morphology of Pt Nanoparticles and Pt-Pd Core-Shell Nanoparticles, Journal of Novel Carbon Resource Sciences, 3, 40-44, 2011.02.
41. N. V. Nong, C.-J. Liu, M. Ohtaki, High Temperature Thermoelectric Properties of Late Rare Earth-doped Ca3Co4-xGaxO9+d
, J. Alloy Compd., 509, 977-981, 2011.01.
42. N. V. Nong, C.-J. Liu, M. Ohtaki, Improvement on the High Temperature Thermoelectric Performance of Ga-doped Misfit-layered Ca3Co4-xGaxO9+d (x = 0, 0.05, 0.1, and 0.2), J. Alloy Compd., 491, 1-2, 53-56, 2010.01.
43. G. Yamamoto, M. Ohtaki, Synthesis and Thermoelectric Properties of Nanoporous Al-doped ZnO, Proc. 11th Cross Straits Symp. Mater. Ener. Environ. Sci., 79-80, 2009.11.
44. K. Yamamoto, M. Ohtaki, Thermoelectric Properties of co-doped ZnO Oxides for Heat-to-Electricity Direct Conversion, Proc. 11th Cross Straits Symp. Mater. Ener. Environ. Sci., 83-84, 2009.11.
45. M. Mori, M. Ohtaki, Molecular Assembly-assisted Synthesis and Photocatalytic Activity of Lamellar Sodium Tantalate, Proc. 11th Cross Straits Symp. Mater. Ener. Environ. Sci., 87-88, 2009.11.
46. S. Teraoka, T. Sugahara, M. Ohtaki, Anomalous Reduction in the Thermal Conductivity of Perovskite-type Oxide on a Structural Phase Transition between the Perovskite and Brownmillerite Structures, Proc. 11th Cross Straits Symp. Mater. Ener. Environ. Sci., 91-92, 2009.11.
47. M. Ohtaki, K. Araki, K. Yamamoto, High Thermoelectric Performance of Dually Doped ZnO Ceramics, Journal of Electronic Materials, 38, 1234-1238, 2009.06.
48. T. Sugahara, M. Ohtaki, T. Souma, Thermoelectric Properties of Double-perovskite Oxide Sr2-xMxFeMoO6 (M = Ba, La), J. Ceram. Soc. Jpn., 116 (12), 1278-1282, 2008.12.
49. T. Souma, D. Isobe, M. Ohtaki, Synthesis and Rietveld Analysis of New Thermoelectric Oxides F-doped Na1.6Co2O4, Trans. Mater. Res. Soc. Jpn., 33 (4), 897-901, 2008.06.
50. T. Souma, M. Ohtaki, K. Ohnishi, M. Shigeno , Y. Ohba, N. Nakamura, T. Shimozaki, Power Generation Characteristics of Oxide Thermoelectric Modules Incorporating Nanostructured ZnO Sintered Materials, Proc. 26th Int. Conf. Thermoelectrics, pp. 38-41, 2008.04.
51. M. Ohtaki, R. Hayashi, K. Araki, Thermoelectric Properties of Sintered ZnO Incorporating Nanovid Structure: Influence of the Size and Number Density of Nanovoids, Proc. 26th Int. Conf. Thermoelectrics, pp. 112-116, 2008.04.
52. T. Sugahara, M. Ohtaki, T. Souma, Thermoelectric Properties of Double-Perovskite Oxide A2B'B"O6 with A-Site Substitution, Proc. 9th Cross Straits Symp. Mater. Ener. Environ. Sci., pp. 137-138, 2007.11.
53. T. Masuda, M. Ohtaki, Suppression of Thermal Conductivity In Metal Oxides Due to Order-Disorder Transition of Oxide Ion Sublattice, Proc. 9th Cross Straits Symp. Mater. Ener. Environ. Sci., pp. 115-116, 2007.11.
54. H. Ikeda, M. Ohtaki, Molecular Templating Electrochemical Synthesis of Nano-Superlattice Thin Films of Layered Oxides and Their Electromagnetic Properties, Proc. 9th Cross Straits Symp. Mater. Ener. Environ. Sci., pp. 95-96, 2007.11.
55. K. Ohnishi, M. Ohtaki, Development of Oxide Thermoelectric Modules with a High Density Packing by Using Ceramic Honeycomb, Proc. 9th Cross Straits Symp. Mater. Ener. Environ. Sci., pp. 63-64, 2007.11.
56. T. Souma, M. Ohtaki, M. Shigeno, Y. Ohba, N. Nakamura, T. Shimozaki, Jointing Technique and Power Generation Characteristics of p-NaCo2O4/n-ZnO Oxide Thermoelectric Modules, Trans. Mater. Res. Soc. Jpn., 32(3), 701-704, 2007.06.
57. T. Souma, M. Ohtaki, M. Shigeno, Y. Ohba, N. Nakamura, T. Shimozaki, Fabrication and Power Generation Characteristics of p-NaCo2O4/n-ZnO Oxide Thermoelectric Modules, Proc. 25th Int. Conf. Thermoelectrics, pp.603-606., 2006.11.
58. T. Souma, M. Ohtaki, Optimization of Synthesis Conditions for CoSb3 Compounds Prepared by Sb Self-flux Method, Proc. 25th Int. Conf. Thermoelectrics, pp.598-602., 2006.11.
59. T. Souma, M. Ohtaki, Relation between Zn Content and Thermoelectric Properties of Zn4+xSb3 (-0.12≦x≦0.12), Proc. 25th Int. Conf. Thermoelectrics, pp.594-597., 2006.11.
60. M. Ohtaki, R. Hayashi, Enhanced Thermoelectric Performance of Nanostructured ZnO: A possibility of Selective Phonon Scattering and Carrier Energy Filtering by Nanovoid Structure, Proc. 25th Int. Conf. Thermoelectrics, pp.276-279., 2006.11.
61. N. V. Nong, M. Ohtaki, Thermoelectric Properties and Local Electronic Structure of Rare Earth-doped Ca3Co2O6, Proc. 25th Int. Conf. Thermoelectrics, pp.62-65., 2006.11.
62. N. V. Nong, M. Ohtaki, Structural Transition and Magnetic Field Induced Strain in Ni50Mn26.5Ga23.5 Alloy, 九州大学大学院総合理工学報告, 28(2), 237-239., 2006.10.
63. N. V. Nong, M. Ohtaki, Power Factors of Late Rare Earth-doped Ca3Co2O6 Oxides, Solid State Commun., 139(5), 232-234., 2006.08.
64. H. Hirobe, M. Ohtaki, Enhanced Phonon Scattering by Oxygen Defects in Metal Oxides, Trans. Mater. Res. Soc. Jpn., 31(2), 403-406., 2006.06.
65. N. V. Nong, M. Ohtaki, High-temperature Thermoelectric properties of Late Rare Earth-doped Ca3Co2O6, Trans. Mater. Res. Soc. Jpn., 31(2), 399-402, 2006.06.
66. T. Souma, M. Ohtaki, Synthesis and Rietveld Analysis of Zn4-xCdxSb3 Bulk Crystals in the Zn-rich Region, J. Alloy. Compd., 413, 289-297, 2006.03.