Study of the Stability of Na0.7CoO2 Thermoelectric Materials under Shock Dynamic Loading in a Shock Tube

  • V. Jayaram
  • C. Shivakumara
  • M. Satyanarayana
  • K. P. J. Reddy
Conference paper


The thermoelectric material is a material that shows large thermo power, low resistivity and low thermal conductivity. Recently, layered cobalt oxides have been extensively investigated as a promising candidate as thermoelectric material. Important feature of sodium cobalt oxides is that, the sodium ions (Na  + ) randomly occupy the regular site by 50% and the sodium content can go up to 70% changes[1]. In this sense layered cobalt oxides, NaCo 2 O 4 should be written as Na x CoO 2 (x = 0.5) and the compound is quite promising for thermoelectric power generation. Terasaki et al. found that a single crystal NaCo 2 O 4 exhibits good thermoelectric property[2]. These layered oxides consist of two layers: CoO 2 layer and Na ion layer. CoO 2 layers acting as an electron reservoir which are responsible for the electrical conductivity and large thermoelectric power. Na ions layer sandwiched between two neighboring CoO 2 layers adjust the concentration of electron in CoO 2 layers and decrease the thermal conductivity along the stacking direction c[3]. Since the discovery of moderately large thermoelectric power (Seebeck coefficient) together with high electrical conductivity in Na x CoO 2(x is 0.70), experiments were done to find new phases for thermoelectric conversion applications[4]. A single-crystal X-ray diffraction study confirmed that Na x CoO 2 (x = 0.74) adopted the hexagonal P63/mmc space group[5]. Neutron diffraction and electron diffraction study shows that the crystal structure of the oxides is strongly dependent on sodium content. The crystal structure of Na 0.75 CoO 2 was studied at ambient and low temperatures down to 10 K at pressures up to 40 GPa using a diamond cell shows an increase in Co-O bond length and decrease in Na-O bond length[6]. Here we present the experimental results on the interaction of shock heated test gases with Na x CoO 2 at high temperature and moderate reflected shock pressure.


Shock Tube Thermoelectric Property Cobalt Oxide Thermoelectric Material Drive Section 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • V. Jayaram
    • 1
  • C. Shivakumara
    • 1
  • M. Satyanarayana
    • 1
  • K. P. J. Reddy
    • 2
  1. 1.Solid State and Structural Chemistry UnitIndian Institute of ScienceBangaloreIndia
  2. 2.Department of Aerospace EngineeringIndian Institute of ScienceBangaloreIndia

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