Thermoelectric phase diagram in a CaTiO3–SrTiO3–BaTiO3 system

Yamamoto, Masahiro; Ohta, Hiromichi; Koumoto, Kunihito

doi:10.1063/1.2475878

Cited by 80 publications

(55 citation statements)

References 13 publications

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“…34 The calculation of the electronic density of states for BiCuSeO indicates a large Seebeck coefficient resulting from a large effective mass (m*). To further verify this assumption, the effective mass (m*) was also calculated according to the following equations using the observed carrier concentration (n) and Seebeck coefficient (S) values 35 :…”

Section: Structural and Thermoelectric Propertiesmentioning

confidence: 99%

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

et al. 2013

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We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu 2 Se 2 ) 2 À and insulating (Bi 2 O 2 ) 2 þ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi 3 þ with Ca 2 þ . The resulting materials exhibit a large positive Seebeck coefficient of B þ 330 lV K À1 at 300 K, which may be due to the 'natural superlattice' layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical conductivity coupled with a moderate Seebeck coefficient leads to a power factor of B4.74 lW cm À1 K À2 at 923 K. Moreover, BiCuSeO shows very low thermal conductivity in the temperature range of 300 (B0.9 W m À1 K À1 ) to 923 K (B0.45 W m À1 K À1 ). Such low thermal conductivity values are most likely a result of the weak chemical bonds (Young's modulus, EB76.5 GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, cB1.5). In addition to increasing the power factor, Ca doping reduces the thermal conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically low thermal conductivity results in a high ZT of B0.9 at 923 K for Bi 0.925 Ca 0.075 CuSeO.

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Section: Structural and Thermoelectric Propertiesmentioning

confidence: 99%

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

et al. 2013

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“…Interestingly, the very first exploration of thermoelectric properties of heavily Nb doped ternary phase diagram of CaTiO 3 -SrTiO 3 -BaTiO 3 was carried out using pulsed laser deposition. 117 Other growth techniques such as sputtering, 118 and molecular beam epitaxy (MBE) 119 were successfully used to grow doped STO films. Especially, MBE grown films demonstrated large cryogenic thermopower due to the phonon drag effect, 120 due to exquisite stoichiometry control.…”

Section: A Titanatesmentioning

confidence: 99%

Thermoelectric and thermal transport properties of complex oxide thin films, heterostructures and superlattices

Ravichandran

2016

J. Mater. Res.

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Over the years, the search for high performance thermoelectric materials has been dictated by the "phonon glass and electron crystal (PGEC)" paradigm, which suggests that low band gap semiconductors with high atomic number elements and high carrier mobility are the ideal materials to achieve high thermoelectric figure of merit. Complex oxides provide alternative mechanisms such as large density of states and strong electron correlation for high thermoelectric efficiency, albeit having low carrier mobility. Due to vast structural and chemical flexibility, they provide a fertile playground to design high efficiency thermoelectric materials. Further, developments in oxide thin film growth methods have enabled synthesis of high quality, atomically precise low dimensional structures such as heterostructures and superlattices. These materials and structures act as excellent model systems to explore nanoscale thermal and thermoelectric transport, which will not only expand the frontier of our knowledge, but also continue to enable cutting edge applications.

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“…1,2) Due to its similarity in the crystal structure, CaTiO 3 is also utilized as a dopant and a member of the superlattice together with other perovskite materials, such as BaTiO 3 and SrTiO 3 . [3][4][5] It has been known that the electric properties and microstructures of those perovskite materials were strongly dependent on the oxygen partial pressure, indicating that defects play an essential role to bring about their properties. [6][7][8][9][10][11][12] Thus, an understanding of defect energetics is indispensable for further developing and applications of these perovskite oxides.…”

Section: Introductionmentioning

confidence: 99%

First Principles Study on Intrinsic Vacancies in Cubic and Orthorhombic CaTiO<SUB>3</SUB>

et al. 2009

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The structural relaxations and the formation energies of intrinsic defects in cubic and orthorhombic CaTiO 3 were investigated by a first principles projector-augmented wave method. It was found that cations and oxygen vacancies in both phases cause extra levels near the valence band maximum and the conduction band minimum, respectively, and the Ti-vacancy induced level in orthorhombic CaTiO 3 is closer to the valence band maximum than that in cubic CaTiO 3 . Among the neutral defect species, including neutral isolated vacancy, partial Schottky, and full Schottky, it was found that the V Ca 2À þ V O 2þ and V O 0 are the most preferable defect species for orthorhombic CaTiO 3 under reduction and oxidization conditions, respectively, whereas the V Ca 2À þ V O 2þ partial Schottky is always stable in any atmosphere in cubic CaTiO 3 . As compared to cubic CaTiO 3 , it was found that orthorhombic CaTiO 3 shows higher defect formation energies.

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Thermoelectric phase diagram in a CaTiO3–SrTiO3–BaTiO3 system

Cited by 80 publications

References 13 publications

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

Thermoelectric and thermal transport properties of complex oxide thin films, heterostructures and superlattices

First Principles Study on Intrinsic Vacancies in Cubic and Orthorhombic CaTiO<SUB>3</SUB>

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