Effect of Copper Additions on the Thermoelectric Properties of a Layered Calcium Cobaltite Prepared by Hot Pressing
- PDF / 2,462,840 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 152 Views
ct of Copper Additions on the Thermoelectric Properties of a Layered Calcium Cobaltite Prepared by Hot Pressing A. I. Klyndyuka, *, I. V. Matsukevichb, M. Janekc, E. A. Chizhovaa, Z. Lenčéšd, O. Hanzeld, and P. Veteškac aBelarusian
State Technological University, Minsk, 220006 Belarus Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Minsk, 220072 Belarus c Slovak University of Technology in Bratislava, Bratislava, SK-812 37 Slovakia d Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, SK-845 36 Slovakia *e-mail: [email protected]
b
Received January 27, 2020; revised June 19, 2020; accepted June 30, 2020
Abstract—Low-porosity layered calcium cobaltite-based ceramics with copper additions have been prepared by hot pressing and their microstructure and electrical transport and thermoelectric properties have been studied. The results demonstrate that the addition of copper particles to the ceramics reduces the average particle size of the Ca3Co4O9 + δ phase and the thermoelectric power and porosity of the samples and increases the electrical conductivity and thermoelectric power factor (P) of the ceramics. The highest thermoelectric power factor is offered by the hot-pressed ceramic with the composition Ca3Co4O9 + δ + 2 wt % Cu (P1100 = 521 μW/(m K2)), which is a factor of 1.4 higher than that of the basic material Ca3Co4O9 + δ having the same thermal history (P1100 = 363 μW/(m K2)) and more than five times the thermoelectric power factor of lowdensity Ca3Co4O9 + δ ceramics prepared by conventional solid-state reactions. Keywords: thermoelectric ceramics, Ca3Co4O9 + δ, Cu, hot pressing, electrical conductivity, thermoelectric power DOI: 10.1134/S0020168520110059
INTRODUCTION The layered calcium cobaltite Ca3Co4O9 + δ is the most promising basic component for designing p-leg materials for high-temperature thermoelectric generators because it offers high electrical conductivity (σ) and thermoelectric power (S) in combination with low thermal conductivity (λ) and is stable in air at high temperatures [1]. The functional characteristics (thermoelectric power factor (P) and thermoelectric figure-of-merit (ZT)) of Ca3Co4O9 + δ-based ceramics are significantly inferior to those of single crystals but can be appreciably improved by using low-temperature (solution phase) synthesis (an alternative to ceramic processing route) [2–5], the preparation of ceramics via hot pressing [3, 6–8] or spark plasma sintering [4, 9, 10], partial bismuth [6, 11, 12] or rare earth [13, 14] substitution for calcium and transition or heavy metal substitution for cobalt [15, 16], and generation of chemical [17] or phase inhomogeneities [18, 19]. Phase inhomogeneities in layered calcium cobaltite-based ceramics can be produced by annealing them at temperatures above the peritectoid decomposition temperature of the Ca3Co4O9 + δ phase (Tp =
1199 K in air [20]); varying the cation stoichiometry of the starting mixture so as to bring the composition of the ceramic beyond the homogeneity r
Data Loading...
