Thermoelectric properties of CaMnO<inf>3</inf> system

Abstract

Ca 1-x RE x MnO 3 (RE: Nd, Tb, Ho, Yb, Lu, x = 0.1 and 0.2) bulks were prepared by a solid state reaction. They show metallic behavior at temperatures higher than about 400 K and electrical resistivity ρ is lower than 12 mΩ cm at 1000 K in air. Absolute values of Seebeck coefficient S increases with temperature up to 973 K for all samples except Ca 0.9 Yb 0.1 MnO 3 at 973 K. For Ca 0.9 Lu 0.1 MnO 3 , S value reaches -130 μV/K at 973 K. Both thermoelectric properties are dominated mainly by crystallographic structure. Power factor PF (=S 2 /ρ) increases with decreasing cell volume.Thermal conductivity κ of Yb-and Lu-substituted samples is as low as 1.5 W/m-K 2 and dimension-less figure of merit ZT reaches 0.16 at 973 K for Ca 0.8 Lu 0.2 MnO 3 in air.

Crystal structure and thermoelectric properties of Sr–Mo substituted CaMnO3: a combined experimental and computational study

“…Un-doped CaMnO 3 also shows a relatively high thermal conductivity of 3.5–2.5 W m –1 K –1 in the temperature range 300–1000 K. The power factor of CaMnO 3 has been enhanced by A-site substitution with different lanthanides. 12 – 14 Similarly, an improved power factor has been achieved by B-site substitution with heterovalent cations including Nb, Ta, W, Ru and Mo through introducing Mn 3+ in the matrix. 10 , 15 – 21 In a study of the effect of Nb and Ta, Xu et al 15 reported a lower resistivity and Seebeck coefficient for Nb doping, achieving a ZT of 0.08 at 1000 K for CaMn 0.96 Nb 0.04 O 3 .…”

High-temperature transport properties of Ca0.98RE0.02MnO3−δ (RE=Sm, Gd, and Dy)

“…In the same vein, increasing the electron carrier concentration of CaMnO 3−␦ can be achieved by partial replacement of Ca 2+ by trivalent metal ions. Ohtaki et al 8 and Funahashi et al 9 studied the effects on the thermoelectric properties of CaMnO 3 by substituting Bi, Y, La, Ce and rare earth ions of Nd, Tb, Ho, Yb, Lu for Ca. They reported that the electrical conductivity increased significantly, while the Seebeck coefficient decreased slightly.…”

Metal oxides for thermoelectric power generation and beyond

“…To this end, the focus of this review article is on examining the metal oxide potentials for TE power generation with an emphasis on materials with high power factor. Effective doping strategies in achieving high power factor are highlighted for various metal oxides, particularly, Na x CoO 2 [15], Ca 3 Co 4 O 9 [16], BiCuSeO [17], CaMnO 3 [18], SrTiO 3 [19], ZnO-based [20], SnO 2 -based [21], and In 2 O 3 -based [22] alloys. More broadly, recent advancement of metal oxides for potential commercial applications in thermal-and electrical-related fields is summarized, which includes TE power generators, solar cells, and sensors.…”