DOI: 10.6060/tcct.20165912.5465
Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2016. V. 59. N 12. P. 87-92

The excessive industry and transport heat can be converted into electrical energy by means of thermoelectric generators (TEG). This provides interest for development of alterna-tive energy sources and also reduces environment "heat pollution". For development of TEG the materials with both high values of electrical conductivity and thermo-EMF coefficient and low thermal conductivity are required. Such complex of properties is observed for ceramics based on layered cobaltites of sodium, calcium and bismuthcalcium. Thermoelectric char-acteristics of oxide ceramics can be enhanced by chemical or phase inhomogenity creation. Thus, effective oxide thermoelectric development in present work Ca2.7Bi0.3Co4O9+–Bi2Ca2Co1.7Oy composite materials had been prepared and investigated as possible materials for p-branches of high-temperature TEG of new generation. (1–x)Ca2.7Bi0.3Co4O9+–xBi2Ca2Co1.7Oy ceramic samples (x = 0.0–1.0) were prepared using solid-state reactions method from CaCO3, Bi2O3 and Co3O4 in air in the temperature range of 1073–1133 K. The samples phase composition was characterized by X-ray diffraction (XRD) analysis using Bruker D8 XRD Advance with monochromatic CuK radiation ( = 1.5406 Å). Thermal ex-pansion, electrical conductivity () and thermo-EMF (Seebeck) coefficient (S) of ceramics were studied in air in the temperature range of 300–1100 K. The power factor values of the samples were calculated using equation P = S2. Ca2.7Bi0.3Co4O9+ (x = 0.0) and Bi2Ca2Co1.7Oy (x = 1.0) samples were monophase, whereas (1–x)Ca2.7Bi0.3Co4O9+–xBi2Ca2Co1.7Oy (x = 0.2–0.8) ceramics was heterogeneous and consisted of Ca2.7Bi0.3Co4O9+ solid solution and layered cobaltite of bismuth–calcium Bi2Ca2Co1.7Oy. The values of linear thermal expansion coefficient (LTEC) varied in the range of (9.82–11.4)10–6 K–1 with a min-imum for the composite with x = 0.6 and minimal LTEC values were observed for ceramics with a predominance of layered bismuth–calcium cobaltite. The obtained materials were p-type conductors and their conductivity changed its character from semiconducting (x  0.6) to metallic (x  0.8) and electrical conductivity values decreased but thermo-EMF coefficient increased with x. The values of Seebeck coefficient and power factor of the samples in-creased with temperature and were maximal for Ca2.7Bi0.3Co4O9+, Bi2Ca2Co1.7Oy and 0.6Ca2.7Bi0.3Co4O9+–0.4Bi2Ca2Co1.7Oy samples – 90–100 W/(mK2) near 1100 K. It was shown that large values of thermo-EMF coefficient of monophase and composite ceramics based on the layered calcium and bismuth–calcium cobaltites indicate the possibility of its usage for high-temperature thermoelectroconversion.

Key words: oxide thermoelectrics, electrical conductivity, thermo-EMF coefficient, power factor, thermal expansion

1. Ioffe A.F. Semiconductor Thermoelements and Thermoelectric Cooling. London: Infosearch. 1957. 184 p.
2. CRC Handbook of Thermoelectrics. Ed. by D.M. Rowe. CRC Press, Boca Raton, FL. 1995. 701 p.
3. Terasaki I., Sasago Y., Uchinokura K. Large thermoelectric power in NaCo2O4 single crystals. Phys. Rev. B. 1997-II. V. 56. N 20. P. R12685–R12687.
4. Thiel P., Populoh S., Yoon S., Weidenkaff A. Enhancement of redox- and phase-stability of thermoelectric CaMnO3–δ by substitu-tion. J. Solid State Chem. 2015. V. 229. P. 62–67. DOI: 10.1016/j.jssc.2015.05.013.
5. Ohta H., Sugiura K., Koumoto K. Recent progress in oxide thermoelectric materials: p-type Ca3Co4O9 and n-type SrTiO3. Inorg. Chem. 2008. V. 47. P. 8429–8436.
6. Sotelo A., Rasekh Sh., Madre M.A., Guilmeau E., Marinel S., Diez J.C. Solution-based synthesis routes to thermoelectric Bi2Ca2Co1.7Ox. J. Eur. Ceram. Soc. 2011. V. 31. P. 1763–1769. DOI: 10.1016/j.jeurceramsoc.2011.03.008.
7. Carvillo P., Chen Y., Boyle C., Barnes P.N., Song X. Thermoelectric performance enhancement of calcium cobaltite through bari-um grain boundary segregation. Inorg. Chem. 2015. V. 54. P. 9027–9032. DOI: 10.1021/acs.inorg-chem.5b01296.
8. Jankowski O., Huber S., Sedmidubsky D., Nadherny L., Hlasek T., Sofer Z. Towards highly efficient thermoelectric: Ca3Co4O9+δ · nCaZrO3 composite. Ceramics – Silikaty. 2014. V. 58. N. 2. P. 106–110.
9. Matsukevich I.V., Klyndyuk A.I., Tugova E.A., Tomkovich M.V., Krasutskaya N.S., Gusarov V.V. Synthesis and properties of materials based on layered calcium and bismuth cobaltites. Russ. J. Appl. Chem. 2015. V. 88. N 8. P. 1241–1247. DOI: 10.1134/S1070427215080030.
10. Gupta R.K., Sharma R., Mahapatro A.K., Tandon R.P. The effect of ZrO2 dispersion on the thermoelectric power factor of Ca3Co4O9. Physica B. 2016. V. 483. P. 48–53. DOI: 10.1016/j.physb.2015.12.028.
11. Klyndyuk A.I., Chizhova Ye.A. Thermoelectric properties of the layered oxides LaBaCu(Co)Fe5+δ (Ln = La, Nd, Sm, Gd). Funct. Mater. 2009. V. 16. N 1. P. 17–22.
12. Klyndyuk A.I., Krasutskaya N.S., Matsukevich I.V., Denisenko M.D., Chizhova Ye.A. Thermoelectric properties of ceramics based on layered sodium and calcium cobaltites. J. Thermoelectricity. 2011. N 4. P. 47–53.

2016, Т. 59, № 12, Стр. 87-92


You will get the pdf-copy of your article by e-mail