High electrical conductivity of layered cobalt oxide Ca3Co4O9 epitaxial films grown by topotactic ion-exchange method

Epitaxial film of a layered cobalt oxide, Ca3Co4O9, was fabricated on a (0001) face of an α-Al2O3 substrate by a topotactic ion-exchange method using a γ-Na0.8CoO2 epitaxial film as a precursor. High-resolution x-ray diffraction and atomic force microscope measurements revealed that the film was high-quality (001)-oriented Ca3Co4O9 with stepped and terraced surface morphology. The film exhibits a high electrical conductivity of 2.95×102Scm−1 and a large Seebeck coefficient of ∼+125μVK−1, which leads to the thermoelectric power factor (TPF) of 4.5×10−4Wm−1K−2 at 300K, potentially usable as a building block of the multilayered film structure with an enhanced TPF value.

[1]  H. Ohta,et al.  Fabrication and thermoelectric properties of layered cobaltite, γ-Sr0.32Na0.21CoO2 epitaxial films , 2006 .

[2]  S. Yamanaka,et al.  Thermoelectric Properties of (Ti,Zr,Hf)CoSb Type Half-Heusler Compounds , 2005 .

[3]  H. Adachi,et al.  Control of Epitaxial Growth Orientation and Anisotropic Thermoelectric Properties of Misfit-Type Ca3Co4O9 Thin Films , 2005 .

[4]  A. Maignan,et al.  Strongly correlated properties of the thermoelectric cobalt oxide Ca 3 Co 4 O 9 , 2005, cond-mat/0505464.

[5]  H. Nozaki,et al.  The formation mechanism of a textured ceramic of thermoelectric [Ca2CoO3](0.62)[CoO2] on beta-Co(OH)2 templates through in situ topotactic conversion. , 2005, Journal of the American Chemical Society.

[6]  Qiang Li,et al.  In situ growth of c-axis-oriented Ca3Co4O9 thin films on Si (100) , 2005 .

[7]  R. Cava,et al.  Spin entropy as the likely source of enhanced thermopower in NaxCo2O4 , 2003, Nature.

[8]  M. Shikano,et al.  Electrical and thermal properties of single-crystalline (Ca2CoO3)0.7CoO2 with a Ca3Co4O9 structure , 2003 .

[9]  Hideo Hosono,et al.  Single‐Crystalline Films of the Homologous Series InGaO3(ZnO)m Grown by Reactive Solid‐Phase Epitaxy , 2003 .

[10]  Y. Miyazaki,et al.  Low-Temperature Synthesis and Electric Properties of New Layered Cobaltite, SrxCoO2 , 2002 .

[11]  Y. Morii,et al.  Modulated Structure of the Thermoelectric Compound [Ca2CoO3]0.62CoO2 , 2002 .

[12]  M. Hervieu,et al.  Misfit-layered cobaltite with an anisotropic giant magnetoresistance: Ca 3 Co 4 O 9 , 2000 .

[13]  Y. Miyazaki,et al.  Low-Temperature Thermoelectric Properties of the Composite Crystal [Ca 2CoO 3.34] 0.614[CoO 2] , 2000 .

[14]  B. Cushing,et al.  Topotactic routes to layered calcium cobalt oxides , 1998 .

[15]  Ichiro Terasaki,et al.  Large thermoelectric power in NaCo 2 O 4 single crystals , 1997 .

[16]  Brian C. Sales,et al.  Thermoelectric Materials: New Approaches to an Old Problem , 1997 .

[17]  H. Ohta,et al.  Reactive Solid-Phase Epitaxial Growth of NaxCoO2 (x ∼ 0.83) via Lateral Diffusion of Na into a Cobalt Oxide Epitaxial Layer , 2005 .

[18]  M. Mikami,et al.  High-throughput screening of thermoelectric oxides and power generation modules consisting of oxide unicouples , 2004 .