Anisotropic electrical transport studies of Ca3Co4O9 single crystals grown by the flux method

Bhattacharya, Shovit; Aswal, D. K.; Singh, Ajay; Thinaharan, C.; Kulkarni, Nilesh; Gupta, S. K.; Yakhmi, J. V.

doi:10.1016/j.jcrysgro.2004.12.142

Cited by 34 publications

(14 citation statements)

References 13 publications

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“…This value is much larger than those reported for 349 single crystals, 2 which can be explained by the following reasons: (i) the in-plane resistivity, r ab , obtained at 300 K for our 349 textured polycrystalline ceramics (6.1 mO.cm) is lower than the values reported for 349 single crystals by Masset et al, 2 (12 mO.cm), and Bhattacharya et al (B19 mO.cm). 26 Our result is in accordance with numerous publications in which comparable values are reported on r ab measurements at 300 K on 349 polycrystalline materials. They also show lower values than those obtained on 349 single crystals.…”

Section: Mechanical and Thermal Propertiessupporting

confidence: 94%

“…For example, reported values are 200 mO.cm 2 and B92.5 mO.cm. 26 The particularly high values found on our bulk materials can be explained by the higher out-plane grain boundary density due to the remarkable decrease of the thickness upon HP at 30 MPa (Table I), and to the strong alignment of the platelets in the ab planes, that is the strong texture resulting from the HP process.…”

Section: Mechanical and Thermal Propertiesmentioning

confidence: 71%

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Anisotropy of the Mechanical and Thermoelectric Properties of Hot-Pressed Single-Layer and Multilayer Thick Ca3Co4O9 Ceramics

Kenfaui

Chateigner

Gomina

et al. 2009

International Journal of Applied Ceramic Technology

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Ca3Co4O9 (349) thermoelectric (TE) ceramics were prepared by hot‐pressing (HP) process under various stress levels up to 30 MPa. Microstructure investigations have revealed strong enhancements of the bulk density and the texture strength, and a remarkable decrease of the in‐plane grain boundary density as the HP stress, σ, is increased. The mechanical properties obtained from nanoindentation and three‐point bending tests, and the TE properties were correlated to the microstructure. The influence of the HP stress level on these properties was examined in the parallel (c) and perpendicular (ab) directions to the pressing axis. Hardness (Hab and Hc ) and elastic modulus (Eab and Ec ) values were shown to increase remarkably with the HP stress level and the anisotropy ratio between out‐of‐plane and in‐plane resistivity values too. As ρab was considerably reduced and the Seebeck coefficient, Sab, remains constant when σ is raised, the power factor, PFab, was greatly improved for the higher stress values. and PFab900 K are 64 and 595 μW.m−1.K−2, respectively, for the HP samples processed under 30 MPa. Thick specimens usable in practical devices were obtained by HP stacked single layers. Their microstructure was investigated and correlated to the TE and mechanical properties.

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Section: Mechanical and Thermal Propertiessupporting

confidence: 94%

Section: Mechanical and Thermal Propertiesmentioning

confidence: 71%

Anisotropy of the Mechanical and Thermoelectric Properties of Hot-Pressed Single-Layer and Multilayer Thick Ca3Co4O9 Ceramics

Kenfaui

Chateigner

Gomina

et al. 2009

International Journal of Applied Ceramic Technology

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“…In the case of misfit-layered Ca 3 Co 4 O 9 single crystals, different anisotropy ratio of electrical transport is reported for crystals prepared by different groups. Masset et al [183] reported an anisotropy in the electrical resistivity of ρ c/ ρ a = 15.5 at room temperature whereas Bhattacharya et al [155] reported a ratio of 4.8. The anisotropic behavior of Seebeck coefficient is less studied in these compounds.…”

Section: Crystallite Alignmentmentioning

confidence: 99%

Thermoelectric power factor: Enhancement mechanisms and strategies for higher performance thermoelectric materials

Dehkordi

Zebarjadi

et al. 2015

Materials Science and Engineering: R: Reports

375

104

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Thermoelectric research has witnessed groundbreaking progress over the past 15-20 years. The thermoelectric figure of merit, ZT, a measure of the competition between electronic transport (i.e. power factor) and thermal transport (i.e. total thermal conductivity), has long surpassed once a longtime barrier of ~1 and thermoelectric scientists are targeting ZT > 2 as the new goal. A majority of this recent improvement in ZT has been achieved through the reduction of lattice part of thermal conductivity ( ) using nanostructuring techniques. The rapid progress in this direction focused the efforts on the development of experimental methods and understanding phonon transport to decrease lattice thermal conductivity. This fact left the development of ideas to improve electronic transport and thermoelectric power factor rather overlooked. With thermal conductivity of the potential thermoelectrics approaching the minimum theoretical limit, on the journey to higher ZT values, a paradigm shift is necessary toward the enhancement of the thermoelectric power factor. This article discusses the ideas and strategies proposed and developed in order to improve the thermoelectric power factor and thus hopefully move us closer to the target of a ZT > 2!

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“…Cobaltite having layered CoO 2 planes and the charge carriers can vary over a remarkably wide range by doping so that effective valence of cobalt ions can change from Co 3 þ to Co 2 þ in these materials. The magnetic properties of yttrium doped Ca 2 Co 2 O 5 are very complicated because of the valence state of cobalt being either 3þ or 2þ due to the misfit between two subsystems in the unit cell [17][18][19][20][21]. The super-exchange and doubleexchange interactions between Co 3 þ and Co 2 þ ions are considered as coexisting in the system.…”

Section: Introductionmentioning

confidence: 99%

Magnetic, optical, microscopic and electrical behavior of Ca2−xYxCo2O5 prepared by a molten flux method

Agilandeswari

Saral

Kumar

2015

Materials Science in Semiconductor Processing

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Anisotropic electrical transport studies of Ca3Co4O9 single crystals grown by the flux method

Cited by 34 publications

References 13 publications

Anisotropy of the Mechanical and Thermoelectric Properties of Hot-Pressed Single-Layer and Multilayer Thick Ca3Co4O9 Ceramics

Anisotropy of the Mechanical and Thermoelectric Properties of Hot-Pressed Single-Layer and Multilayer Thick Ca3Co4O9 Ceramics

Thermoelectric power factor: Enhancement mechanisms and strategies for higher performance thermoelectric materials

Magnetic, optical, microscopic and electrical behavior of Ca2−xYxCo2O5 prepared by a molten flux method

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