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A2: Medium temperature materials

Thermoelectric Properties of LiNiO2-NiO Multicomponent Ceramics

Takuto Kawano1, Hirofumi Kakemoto1 and Hiroshi Irie1
1Univ. of Yamanashi

Thermoelectric (TE) generation is attracted as renewable energy resource from waste heat. The oxide TE material, NaxCoO2 (NCO)1, shows high ZT up to 0.8 comparable to widely accepted Bi2Te3. However the number of oxide TE materials with high ZT is limited. Here, we suppose the improvement of TE properties based on percolation theory.2 We selected LiNiO2 (LNO) and NiO. LNO has been utilized as electrodes for Li ion battery, thus high electrical conductivity (σ) can be expected, whereas, NiO is an insulator. The mixture of NiO and LNO particles would be applied to the percolation theory for σ, and thus it would be possible to control TE properties. We attempted to optimize the ratio of the two compounds.

LNO was prepared by the conventional solid state reaction with an optimum amount of Li2CO3, LiOH・H2O and NiO as raw materials.3 The ratio of LNO and NiO was changed by controlling the amounts of starting materials and sintering atmosphere (oxygen or air). The LNO and NiO ratio was determined by X-ray diffraction, calculating the ratio of the strongest peak of the two compounds. The Seebeck coefficient (S) and σ were measured by quasi-steady state method from 100 to 600 °C.

S and σ of LNO-NiO multiphase samples increased and decreased, respectively, with increasing NiO content. This is a typical behavior in accordance with the Ioffe theory. In addition, σ suddenly increased below the NiO content of 50 mol%, where the electrical conductive path formed, accompanying the decrease in S. This indicates that the TE properties could improve by optimization of LNO-NiO ratio.

 

  1. I. Terasaki et al., Phys. Rev. B 56, R12685(1977)
  2. J. Yang et al., Adv. Eng. Mater, 9, 5(2003)
  3. G. X. Wang, et al., J. Power Sources, 76, 141(1998)