Thermoelectric transport in the layered Ca3Co4–<i>x</i>Rh<i>x</i>O9 single crystals

Ikeda, Yusuke; Saito, Kengo; Okazaki, Renji

doi:10.1063/1.4953359

Cited by 13 publications

(9 citation statements)

References 47 publications

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“…In the metallic samples for y ≥ 0.06, as shown in Fig. 2(c), the low-temperature resistivity shows a Fermi-liquid behavior ρ(T ) = ρ 0 + AT 2 with a small upturn below 20 K, as is similar to the polycrystalline study [19] and to the results of other layered oxides [31][32][33][34]. The doping dependence of A will be mentioned later.…”

Section: Resultssupporting

confidence: 81%

Correlation in transport coefficients of hole-doped CuRhO2 single crystals

2019

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To clarify the origin of the nontrivial thermoelectric properties observed in the delafossite oxide CuRhO 2 polycrystals, we have performed the systematic transport measurements on the single-crystalline CuRhO 2 samples. In the parent compound, we find a pronounced peak structure due to a phonon-drag effect in the temperature dependence of the Seebeck coefficient, which is also confirmed by the size effect experiments. In the Mg-substituted crystals, in contrast to the results of the polycrystals, both the resistivity and the Seebeck coefficient decrease with increasing Mg content y. In particular, the coefficient A for the T 2 term of the resistivity and the T -linear coefficient for the Seebeck coefficient at low temperatures are well described within a simple relationship expected for metals, which is also applicable to the correlated materials with low carrier densities.

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Section: Resultssupporting

confidence: 81%

Correlation in transport coefficients of hole-doped CuRhO2 single crystals

2019

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“…The thermoelectric voltage of the sample was measured with Keithley 2182A nanovoltmeter. The temperature gradient was measured with a differential thermocouple made of copper and constantan in a liquid He cryostat below 300 K and with two platinum temperature sensors in a hightemperature equipment from 300 K to 700 K [37,38]. In both measuring apparatuses, the thermoelectric voltage from the wire leads was subtracted.…”

Section: Methodsmentioning

confidence: 99%

Prominent electron-hole asymmetry in thermoelectric transport of LaCoO3

Okazaki

Tomiyasu

2022

Phys. Rev. B

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We have measured the electrical resistivity and the thermopower of the electron-doped perovskite cobaltites LaCo 1−y Te y O 3 . In contrast to the hole-doped systems such as metallic ferromagnets La 1−x M x CoO 3 (M = Ca, Sr, Ba), the electron-doped samples show an insulating behavior even in a heavily doped range due to a spin-state blockade mechanism that an electron hopping from high-spin Co 2+ to low-spin Co 3+ site is energetically suppressed. We find that, despite the electron doping, the thermopower shows relatively large positive values above y = 0.05, strikingly distinct from the hole-doped case where it comes close to zero with doping. This prominent electron-hole asymmetry seen in the thermopower originates from a bipolar conduction which consists of a slight amount of mobile holes and the main immobile electrons, demonstrating an impact of spin-state blockade on thermoelectric transport.

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“…Single crystals of [Ca 2 CoO 3 ] 0.62 [CoO 2 ] were grown by a flux method [33]. Powders of CaCO 3 (99.9%) and Co 3 O 4 (99.9%) were mixed in a stoichiometric ratio and calcined two times in air at 1173 K for 20 h with intermediate grindings.…”

Section: Methodsmentioning

confidence: 99%

Crossover from itinerant to localized states in the thermoelectric oxide [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$]

Sakabayashi,

Okazaki

2021

Preprint

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The layered cobaltite [Ca 2 CoO 3 ] 0.62 [CoO 2 ], often expressed as the approximate formula Ca 3 Co 4 O 9 , is a promising candidate for efficient oxide thermoelectrics but an origin of its unusual thermoelectric transport is still in debate. Here we investigate in-plane anisotropy of the transport properties in a broad temperature range to examine the detailed conduction mechanism. The in-plane anisotropy between a and b axes is clearly observed both in the resistivity and the thermopower, which is qualitatively understood with a simple band structure of the triangular lattice of Co ions derived from the angle-resolved photoemission spectroscopy experiments. On the other hand, at high temperatures, the anisotropy becomes smaller and the resistivity shows a temperature-independent behavior, both of which indicate a hopping conduction of localized carriers. Thus the present observations reveal a crossover from low-temperature itinerant to high-temperature localized states, signifying both characters for the enhanced thermopower.

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Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Cited by 13 publications

References 47 publications

Correlation in transport coefficients of hole-doped CuRhO2 single crystals

Correlation in transport coefficients of hole-doped CuRhO2 single crystals

Prominent electron-hole asymmetry in thermoelectric transport of LaCoO3

Crossover from itinerant to localized states in the thermoelectric oxide [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$]

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