Thermoelectric Properties of Ca3Co4O9-Based Ceramics Doped with Fe and/or Y

A.S. Fedotova, A.K. Fedotova, A.V. Mazanika, I.A. Svitoa, A.M. Saadb, I.O. Troyanchukc, M.V. Bushinskic, V.V. Fedotovac, P. Zukowskid and T.N. Koltunowiczd aBelarusian State University, Independence av. 4, 220030 Minsk, Belarus bAl-Balqa Applied University, P.O. Box 4545, Amman 11953, Jordan cScientific-Practical Materials Research Center of NASB, 220072 Minsk, Belarus dDepartment of Electrical Devices and High Voltages Technologies, Lublin University of Technology, Nadbystrzycka 38a, 20-618 Lublin, Poland

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We describe here structure and temperature dependences of conductivity σ(T), the Seebeck coefficient α(T), thermal conductivity λ(T) and figure-of-merit ZT(T) in Ca3Co4O9 ceramics, doped with Fe and Y, depending on compacting pressure (0.2 or 6 MPa) and temperature (300 < T < 700 K). It is shown that introduction of iron and yttrium to ceramics does not alter the crystalline structure of the material. Increasing the pressure in the compacting process before the additional diffusion annealing leads to a smaller-grained structure and increase σ and λ due to reducing of the synthesized samples porosity. The Seebeck coefficients of nanocomposite ceramics Ca3Co3.9Fe0.1O9 and (Ca2.9Y0.1)(Co3.9Fe0.1)O9 have linear dependences on temperature is not changed after increase of compacting pressure. Electrical-to-heat conductivity ratio (σ/λ) for the samples compacted at high (6 GPa) pressure increases not more than 20-30% in comparison with ones compacted at low (0.2 GPa) pressure, whereby ZT is increased more than 50%. The main reason for this effect is samples porosity reduction with the compacting pressure increase.

DOI: 10.12693/APhysPolA.125.1344 PACS numbers: 46.25.Hf, 62.20.D-, 82.45.Xy