High-temperature thermoelectric properties of Ca0.9−xSrxYb0.1MnO3−δ (≤x≤0.2)

Abstract

Polycrystalline samples of Ca0.9−xSrxYb0.1MnO3−δ (x=0, 0.025. 0.05, 0.1, and 0.2) were prepared by a conventional solid-state reaction and their thermoelectric properties were evaluated at 303–973 K. Each of the samples consisted of a single phase with an orthorhombic structure. All the samples showed a metallic conductivity and their electrical resistivity was markedly affected by the distortion of the MnO6 octahedron. The Seebeck coefficient of all the samples was negative, indicating that the predominant carriers were electrons over the entire temperature range examined. The highest power factor achieved (0.22 mW m−1 K−2 at 773 K) was shown by the sample with x=0.1. The thermal conductivity was affected by both the crystal distortion and the difference in mass between the Ca2+ and Sr2+ ions. The highest dimensionless figure of merit obtained was 0.09 at 973 K for the sample with x=0.1; this is a result of its low electrical resistivity and its moderate Seebeck coefficient and thermal conductivity.

Effects of Dy and Yb co-doping on thermoelectric properties of CaMnO3 ceramics

“…By recalling the lattice parameters shown in Table. 1, it can be found that the Seebeck coefficient decreases with the increase of the lattice parameters. Similar behavior has also been observed in samples of Sr/Yb dual doped CaMnO 3 ceramics [20]. The Seebeck coefficients of doped samples are nearly linear function of temperature from 300 K to 1100 K. The linear relationship of Seebeck coefficients with temperature, in accord with the behavior reported before [11,12], implies a metallic behavior of the electron conduction.…”

“…With the doping content increased, total thermal conductivity increases. This behavior is also observed in Sr and Yb co-doped CaMnO 3 [20], [16] and 68% to Yb-doped CaMnO 3 [15]. Also, the highest value 11 of ZT is about five times larger than that of un-doped CaMnO 3 sample.…”

Synthesis of Dy doped Yb0.1Ca0.9MnO3 ceramics with a high relative density and their thermoelectric properties

“…Therefore, several researchers have made extensive studies on oxide materials. For instance, the p-type Co-based layered oxides [2][3][4] and n-type perovskite oxide (SrTiO 3 , CaMnO 3 etc [5][6][7][8]). In general, the figure of merit for p-type oxide is higher than that of n-type.…”

High-temperature thermoelectric properties of Ca0.9Y0.1Mn1−x Fe x O3 (0 ≤ x ≤ 0.25)

“…Many attempts have been 54 made in order to improve the thermoelectric performance 55 of this type of material, mainly to enhance the electrical 56 conductivity, reduce further the thermal conductivity, 57 while avoiding degradation of the Seebeck coefficient. 58 Most of these studies have been focused on doping, for 59 example, Yb at Ca-site [4][5][6][7] or Nb at Mn-site [3,8], while 60 only few reports performed the research on dually doping, 61 e.g., Sr and Yb at Ca-site [9]. Previous reports have showed 62 that the substitution of Y for Ca resulted in a significant 63 improvement in the thermoelectric performance of Ca 12x 64 Y x MnO 3 system in a wide temperature region, and the 87 (99.9 %) precursors were thoroughly mixed by ball milling 88 with ethanol for 24 h. The mixtures were dried and then 89 calcined at 1273 K for 24 h in air with an intermediate 90 grinding procedure.…”

“…For 48 this purpose, metal oxide-based materials are considered as 49 good candidates. 50 CaMnO 3 , which is a perovskite oxide with orthorhombic 51 structure at room temperature, has also been considered as 52 a promising thermoelectric n-type material for high-53 temperature application [3][4][5][6][7][8][9]. Many attempts have been 54 made in order to improve the thermoelectric performance 55 of this type of material, mainly to enhance the electrical 56 conductivity, reduce further the thermal conductivity, 57 while avoiding degradation of the Seebeck coefficient.…”