Anisotropic Heat Conduction in Ion‐Substituted Layered Cobalt Oxides

Cho, Hai Jun; Takashima, Yugo; Nezu, Yukio; Onozato, Takaki; Ohta, Hiromichi

doi:10.1002/admi.201901816

Cited by 17 publications

(17 citation statements)

References 47 publications

(106 reference statements)

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“…Although Na 0.75 CoO 2 is expected as a practical thermoelectric material, 210) the ZT was only about 0.03 due to its high ¬. 213) Cho et al 214) considered the strategy as shown in Fig. 13 to reduce the ¬ of the layered cobalt oxide A x CoO 2 .…”

Section: Record-high Room Temperature Thermoelectric Figure Of Merit ...mentioning

confidence: 99%

Ceramic science of crystal defect cores

Matsunaga

Yoshiya

Shibata

et al. 2022

J. Ceram. Soc. Japan

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Point defects, dislocations, grain boundaries and interfaces are always involved in ceramic microstructures and play important roles for physical and chemical properties of ceramics. Currently, proper control of these crystal defects is inevitable to tailor ceramic materials with superior properties. This article reviews recent research projects on distinct properties and phenomena in ceramics due to crystal defects. In particular, we would like to emphasize importance of central core regions of crystal defects, namely, "crystal defect cores". They have specific electronic and atomic structures that are different from those in bulk. Recent advances of nanoscale characterizations and theoretical calculations make it possible to acquire a variety of quantitative data on electronic structures enclosed at the crystal-defect cores, which gives clear understanding of various ceramic properties at the electronic and atomic levels.

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Section: Record-high Room Temperature Thermoelectric Figure Of Merit ...mentioning

confidence: 99%

Ceramic science of crystal defect cores

Matsunaga

Yoshiya

Shibata

et al. 2022

J. Ceram. Soc. Japan

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“…In conventional material systems, heavier atoms usually suppress lattice vibrations and decrease κ. 16 However, the κ of SrSnO3 (Sr = 87.62 amu) is lower than that of BaSnO3 (Ba = 137.33 amu). This suggests that the κ of Ba1−xSrxSnO3 solid solution films is dominated by a different factor.…”

Section: Resultsmentioning

confidence: 93%

“…Thermal conductivity usually decreases with increasing atomic mass. 16 However, although Sr (87.62 amu) is lighter than Ba (137.33 amu), the thermal conductivity of SrSnO3 was much lower than that of BaSnO3, confirming all transport properties are dominated by the deviation from a cubic phase. These contributions reveal a fundamental factor that affects the transport properties in ASnO3, which are of significant importance for engineering their transport properties in various applications.…”

Section: Introductionmentioning

confidence: 88%

Effect of lattice distortions on the electron and thermal transport properties of transparent oxide semiconductor Ba1 − xSrxSnO3 solid solution films

Cho

Sato

Wei

et al. 2020

Journal of Applied Physics

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La-doped ASnO3 (A = Ba, Sr) have great potential as advanced transparent oxide semiconductors due to their large optical bandgap and relatively high electron mobility. The bandgap of Ba1−xSrxSnO3 solid solution increases from 3.2 eV (BaSnO3) to 4.6 eV (SrSnO3) with x. However, the increase in the bandgap is accompanied by reductions in the electrical conductivity. The versatility in the changes in the electrical properties are not trivial, and the property optimization has been challenging. Here we propose a simple metric for quantifying the transport properties of ASnO3. We investigated the electron/thermal transport properties of Ba1−xSrxSnO3 solid solution films and their relationship with the lattice distortion. The results suggest that the all transport properties of Ba1−xSrxSnO3 are dominated by the lattice distortion. This phenomenon is attributed to the distortions in the SnO6 octahedron, which consists the conduction band. I.Rietveld analyses of the powder diffraction patterns of the Ba1−xSrxSnO3 PLD target ceramics. We found that the space group of x ≤ 0.5 is Pm-3m (cubic perovskite) whereas x ≥ 0.7 is Pnma (orthorhombic perovskite) ( Supplementary Fig. S5). The crystal structures drawn from the Rietveld analysis results also demonstrate that the lattice distortion at x = 0.7 is much greater than that at x = 1 (Supplementary Fig. S6). These results would indicate that the lattice distortion is spontaneously introduced due to the stability of orthorhombic symmetry around x ~0.7.Interestingly, the changes observed in the lattice distortion are similar with those observed from the electron and thermal transport properties. In the undoped Ba1−xSrxSnO3 solid solution system, BaSnO3 (x = 0) initially exhibits a near-perfect cubic structure, where the κ is the highest (8 W m −1 K −1 ). The lattice distortion gradually increases until x = 0.7, where the κ exhibits a minimum ( Fig. 3 and 5b). As x increases further, the lattice distortion gradually reduces until x = 1 (SrSnO3). Since the bowing of lattice parameters occurred in the BaSnO3 -SrSnO3 solid solution system like BaTiO3 -SrTiO3 system 21 , the lattice distortion was maximized around x = 0.7, and the cubic structure is not fully recovered, which is consistent with the κ of SrSnO3 being lower than that of BaSnO3. In the case of La-doped Ba1−xSrxSnO3 solid solution films, the lattice distortion has an increasing tendency until x = 0.8 and decrease as it approaches x = 1, which is consistent with all electron transport properties ( Fig. 4 and 5d). However, unlike the lattice distortion, a plateau can be seen in μHall and n from x = 0.2 to 0.4. This plateau implies that the dopant scatterings from the A-site substitution is not significant but not trivial to understand. It seems that ~0.6 % is a critical distortion in SnO6 for the electron transport properties of ASnO3. For example, a sudden drop in μHall and n is observed at x = 0.5 when the lattice distortion reaches ~0.7 %. In addition, an abrupt 9 S. Raghavan, T.

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“…The observed κ values using the latter films can be decomposed into the κ perpendicular to the superlattice (κ ⊥ ) and parallel (κ // ) to the superlattice. Thus, we extracted the κ // using the following equation [ 30,31 ]

\begin{matrix} κ_{obsd} = \sqrt{κ_{⊥}^{2} \cos^{2} θ + κ_{∥}^{2} \sin^{2} θ} \end{matrix}

where θ is 31.5°.…”

Section: Figurementioning

confidence: 99%

Anomalously Low Heat Conduction in Single‐Crystal Superlattice Ceramics Lower Than Randomly Oriented Polycrystals

Cho

Zhang

et al. 2021

Adv Materials Inter

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Heat conduction in ceramics is attributed to phonon propagation, which can be strongly suppressed at boundaries. Usually, polycrystals show lower thermal conductivity (κ) than single crystals, as polycrystals contain many grain boundaries. For functional applications in thermal management technologies, ceramics with low thermal conductivity are required. While grain boundary engineering is effective for reducing κ, its utilization is limited by the fact that other functional properties are often damaged. Here it is shown that single‐crystalline oxide of InGaO3(ZnO)m with a natural superlattice structure exhibits anomalously lower κ than polycrystals. Single‐crystalline films of InGaO3(ZnO)m (m = integer), which has a superlattice structure of InO2−/GaO(ZnO)m+ stacking along the c‐axis with a controllable layer thickness of m, are fabricated. It is found that the κ perpendicular to the superlattices decreases with decreasing m‐value, and the minimum κ is 1.1 W m−1 K−1 (m = 4, 5), which is lower than randomly oriented polycrystalline InGaO3(ZnO)m. On the other hand, the κ parallel to the superlattices have similar values with those of polycrystalline. The present finding suggests that layer boundaries between different components inside single crystal can also function as thermal resistance, which will be useful for the material design of thermal management technologies.

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Anisotropic Heat Conduction in Ion‐Substituted Layered Cobalt Oxides

Cited by 17 publications

References 47 publications

Ceramic science of crystal defect cores

Ceramic science of crystal defect cores

Effect of lattice distortions on the electron and thermal transport properties of transparent oxide semiconductor Ba1 − xSrxSnO3 solid solution films

Anomalously Low Heat Conduction in Single‐Crystal Superlattice Ceramics Lower Than Randomly Oriented Polycrystals

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