Magnetic field enhanced thermal conductivity and origin of large thermopower in layered cobaltates

Impact of Oxygen Stoichiometry on the Thermoelectric Properties of Bi2Sr2Co2Oy Thin Films

“…Layered materials offer significant potential for the development of highly efficient thermoelectric (TE) materials due to their directional TE properties, such as anisotropic thermal conductivity, − and high in-plane TE power factor. − In particular, layered cobaltates (e.g., Na x CoO 2 , Ca 3 Co 4 O 9 , Bi 2 Sr 2 Co 2 O y , and La 2– x Sr x CoO 4 ) have emerged as promising p-type materials for TE application due to (i) their unique combination of electronic and thermal properties, − (ii) earth abundance of their constituent elements, (iii) high temperature stability, and (iv) the nontoxic nature of their constituent elements compared to commercial materials, e.g., Bi 2 Te 3 . These materials exhibit complex behaviors arising from the interplay of charge, spin, and lattice vibrations, making them highly versatile for energy conversion applications. ,, A worth noting advantage of cobaltates is their intrinsic high in-plane electrical conductivity (σ), coupled with low thermal conductivity ( k ) and high Seebeck coefficient ( S ), − enabling them to produce significant voltage differences when exposed to temperature gradients. An additional advantage lies in the particular misfit crystal structure of this class of layered cobaltates, which results in anisotropic thermal properties with low in-plane ( k ∥ = 6–1.5 W m –1 K –1 ) − and out-of-plane ( k ⊥ = 1–0.07 W m –1 K –1 ) − thermal conductivities.…”

“…Layered materials offer significant potential for the development of highly efficient thermoelectric (TE) materials due to their directional TE properties, such as anisotropic thermal conductivity, 1 − 3 and high in-plane TE power factor. 4 − 6 In particular, layered cobaltates (e.g., Na x CoO 2 , Ca 3 Co 4 O 9 , Bi 2 Sr 2 Co 2 O y , and La 2– x Sr x CoO 4 ) have emerged as promising p-type materials for TE application due to (i) their unique combination of electronic and thermal properties, 7 − 10 (ii) earth abundance of their constituent elements, (iii) high temperature stability, and (iv) the nontoxic nature of their constituent elements compared to commercial materials, e.g., Bi 2 Te 3 . These materials exhibit complex behaviors arising from the interplay of charge, spin, and lattice vibrations, making them highly versatile for energy conversion applications.…”

“…These materials exhibit complex behaviors arising from the interplay of charge, spin, and lattice vibrations, making them highly versatile for energy conversion applications. 7 , 11 , 12 A worth noting advantage of cobaltates is their intrinsic high in-plane electrical conductivity (σ), coupled with low thermal conductivity ( k ) and high Seebeck coefficient ( S ), 13 − 21 enabling them to produce significant voltage differences when exposed to temperature gradients. An additional advantage lies in the particular misfit crystal structure of this class of layered cobaltates, which results in anisotropic thermal properties with low in-plane ( k ∥ = 6–1.5 W m –1 K –1 ) 22 − 25 and out-of-plane ( k ⊥ = 1–0.07 W m –1 K –1 ) 23 − 26 thermal conductivities.…”