Effects of addition of Bi2Ca2Co2O y on the thermoelectric properties of Ca3Co4O9 polycrystalline ceramics

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2018-06, Vol.124 (6), p.1-7, Article 432
• Main Authors: Feng, Ningbo, Liao, Y. W., Lu, Y., He, Y., Jin, Y. R., Liu, X. R.
• Format: Article
• Language: English
• Subjects: Applied physics; Bulk density; Ceramics; Composite materials; Constitution; Electrical resistivity; Materials science; Polycrystals; Power factor; Seebeck effect; Thermal conductivity; Thermoelectricity
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-018-1860-6

Thermoelectric properties of Ca3Co4O9 polycrystalline ceramics with sheet grains were optimized by adding Bi2Ca2Co2Oy phase. Therefore, the (1 − x) Ca3Co4O9/x Bi2Ca2Co2Oy (0 ≤ x ≤ 1) composites were prepared. The phase constitution and micro-structure of the samples were analyzed by XRD and SEM, respectively. With the addition of Bi2Ca2Co2Oy, the apparent density Da and the relative density Dr of the samples continuously increases. When x ≤ 0.4, the electrical resistivity of the samples declines, however, when x ≥ 0.4, the electrical resistivity of the samples increases. The Seebeck coefficient of the samples grows with the increase of the x monotonously. The power factor of the 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2Oy samples reaches 0.24 mW m−1K−2 at 973 K. Thermal conductivity κ of the 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2Oy monotonously decreases with the temperature rising, achieving the minimum about 1.34 W m−1K−1 at 973 K. The ZT of 0.6 Ca3Co4O9/0.4 Bi2Ca2Co2Oy composites gets to 0.18, which is comparable to that of most doped Ca3Co4O9 polycrystalline ceramics, implying higher ZT can be realized by combining the strategy of doping and introducing the Bi2Ca2Co2Oy.