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

Introduction

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.

Keywords

Shock Tube Thermoelectric Property Cobalt Oxide Thermoelectric Material Drive Section 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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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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