Thermoelectric properties of Bi2Sr2Co2Oy thin films and single crystals

Abstract

Bi 2 Sr 2 Co 2 O 9 exhibits a misfit-layered structure with good thermoelectric properties. We have investigated the thermoelectric properties of Bi 2 Sr 2 Co 2 O y in both thin-film and single-crystal forms. Among thin films grown at different temperatures, we find that both the in-plane thermoelectric power (S ab ) and electrical resistivity ( ab ) vary in an opposite trend, i.e., S ab is high when  ab is small. This results in large power factor (S ab 2 / ab ~ 5.5 W/K 2 cm for the film grown at 700 C), comparable to that for whiskers. For single crystals, the electrical resistivity shows metallic behavior in a large temperature range, but has higher magnitude than that of films grown at 675 C and 700 C. The annealing of single crystals under Ar atmosphere leads to even higher resistivity while S ab is improved.We discuss the thermoelectric performance of this material considering both oxygen concentration and phase purity.

Improvement of grain alignment in Bi2Sr2Co1.8Oy thermoelectric through the electrically assisted laser floating zone

“…Nevertheless, these samples display the lowest thermal conductivity, clearly indicating that passing a DC during the growth process can effectively increase phonon scattering, playing a major role in thermal conductivity [36]. [38], and slightly lower than that obtained in thin films (0.09 at 150 °C) [39]. On the other hand, these values are very low when compared with Bi-Sr-Co-O/Ag composites (0.26 at 700 °C) [40], as summarized in Table 5.…”

Enhanced Thermoelectric Properties of Misfit Bi2Sr2-xCaxCo2Oy: Isovalent Substitutions and Selective Phonon Scattering

“…However, the lower κ for polycrystalline samples reflects the important contribution of phonon scattering at the grain boundaries. In the literature, a large discrepancy in the absolute value of the thermal conductivity of BSCO polycrystals and single crystal is observed, which varies from ~0.8 to ~4 W/mK at 300 K. This variation is attributed to the different methods of sample preparation [ 19 , 27 ], measurement techniques [ 20 , 21 , 45 ], as well as the sintering process followed before measurements [ 32 ]. A comparison of the reported κ at 300 K is presented in Table 1 .…”

Thermoelectric Properties of Misfit Layered Bismuth-Based Rhodium Oxides, (Bi,Pb)<sub>2</sub>Sr<sub>2</sub>Rh<sub>2</sub>O<sub>y</sub>

“…Note that the reported Rh 3d 5/2 binding energies are 308.1 eV for hexagonal Rh 2 O 3 (Rh 3+ ), 308.3 eV for orthorhombic Rh 2 O 3 (Rh 3+ ), and 309.4 eV for tetragonal RhO 4 (Rh 4+ ) [22]. gives the smaller S value by Heike's formula [14] [20]. The Pb substitution led to the enhancement of the ZT value up to 0.067.…”