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1. Thermal properties and lattice anharmonicity of Li-ion conducting garnet solid electrolyte Li _6.5 La ₃ Zr _1.5 Ta _0.5 O ₁₂

   https://doi.org/10.1039/d4ta02264e  

   Wang, Yitian; Li, Shuchen; Wu, Nan; Jia, Qianru; Hoke, Thomas; Shi, Li; Li, Yutao; Chen, Xi (July 2024, Journal of Materials Chemistry A)

   This work reports the thermal properties of garnet electrolyte LLZTO. The aged LLZTO exhibits an enhanced thermal conductivity, attributed to the formation of Li₂CO₃. 

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2. Comparative Thermal Insulation Nature of Ca ₂ FeMnO _6−δ and Sr ₂ FeMnO _6−δ

   https://doi.org/10.1149/2754-2734/ad27dc  

   Schultz, Ebony; Guinn, Mandy; Azure, Alexa D.; Hona, Ram Krishna (February 2024, ECS Advances)

   In this study, we investigate the utility of Ca₂FeMnO_6-δand Sr₂FeMnO_6-δas materials with low thermal conductivity, finding potential applications in thermoelectrics, electronics, solar devices, and gas turbines for land and aerospace use. These compounds, characterized as oxygen-deficient perovskites, feature distinct vacancy arrangements. Ca₂FeMnO_6-δadopts a brownmillerite-type orthorhombic structure with ordered vacancy arrangement, while Sr₂FeMnO_6-δadopts a perovskite cubic structure with disordered vacancy distribution. Notably, both compounds exhibit remarkably low thermal conductivity, measuring below 0.50 Wm⁻¹K⁻¹. This places them among the materials with the lowest thermal conductivity reported for perovskites. The observed low thermal conductivity is attributed to oxygen vacancies and phonon scattering. Interestingly as SEM images show the smaller grain size, our findings suggest that creating vacancies and lowering the grain size or increasing the grain boundaries play a crucial role in achieving such low thermal conductivity values. This characteristic enhances the potential of these materials for applications where efficient heat dissipation, safety, and equipment longevity are paramount. 

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3. Structural and thermal properties of ultralow thermal conductivity Ba ₃ Cu ₂ Sn ₃ Se ₁₀

   https://doi.org/10.1039/d2dt00309k  

   Ojo, Oluwagbemiga P.; Gunatilleke, Wilarachchige D.; Wang, Hsin; Nolas, George S. (April 2022, Dalton Transactions)

   The thermal properties of Ba 3 Cu 2 Sn 3 Se 10 were investigated by measurement of the thermal conductivity and heat capacity. The chemical bonding in this diamagnetic material was investigated using structural data from Rietveld refinement and calculated electron localization. This quaternary chalcogenide is monoclinic ( P 2 1 / c ), has a large unit cell with 72 atoms in the primitive cell, and a high local coordination environment. The Debye temperature (162 K) and average speed of sound (1666 m s −1 ) are relatively low with a very small electronic contribution to the heat capacity. Ultralow thermal conductivity (0.46 W m −1 K −1 at room temperature) is attributed to the relatively weak chemical bonding and intrinsic anharmonicity, in addition to a large unit cell. This work is part of the continuing effort to explore quaternary chalcogenides with intrinsically low thermal conductivity and identify the features that result in a low thermal conductivity. 

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4. Thermal Conductivity of MgSiO ₃ ‐H ₂ O System Determined by Machine Learning Potentials

   https://doi.org/10.1029/2023GL107245  

   Peng, Yihang; Deng, Jie (March 2024, Geophysical Research Letters)

   Abstract Thermal conductivity plays a pivotal role in understanding the dynamics and evolution of Earth's interior. The Earth's lower mantle is dominated by MgSiO₃polymorphs which may incorporate trace amounts of water. However, the thermal conductivity of MgSiO₃‐H₂O binary system remains poorly understood. Here, we calculate the thermal conductivity of water‐free and water‐bearing bridgmanite, post‐perovskite, and MgSiO₃melt, using a combination of Green‐Kubo method with molecular dynamics simulations based on a machine learning potential of ab initio quality. The thermal conductivities of water‐free bridgmanite and post‐perovskite overall agree well with previous theoretical and experimental studies. The presence of water mildly reduces the thermal conductivity of the host minerals, significantly weakens the temperature dependence of the thermal conductivity, and reduces the thermal anisotropy of post‐perovskite. Overall, water reduces the thermal conductivity difference between bridgmanite and post‐perovskite, and thus may attenuate lateral heterogeneities of the core‐mantle boundary heat flux. 

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5. Intrinsic thermal expansion and tunability of thermal expansion coefficient in Ni-substituted Co ₂ V ₂ O ₇

   https://doi.org/10.1088/2515-7639/acfdce  

   Esteban, Erica T. B.; Garcia, Jasmine J.; Windover, Sophie R.; Cooley, Joya A. (October 2023, Journal of Physics: Materials)

   Abstract Framework oxide materials are well-known for exhibiting not only negative thermal expansion (NTE), but also demonstrating thermal expansion that can be controlled using composition as a tuning parameter. In this work, we study the intrinsic thermal expansion properties of Co₂V₂O₇, which has shown bulk linear NTE, and attempt to understand how substituting Ni²⁺for Co²⁺will affect the thermal expansion. The isomorphic solid solution is synthesized through solid-state methods and characterized using x-ray diffraction (XRD), diffuse reflectance spectroscopy, and neutron diffraction. The size difference between Ni²⁺and Co²⁺as well as the polyhedral volume of each Co²⁺metal coordination environment in the crystal structure allows Ni²⁺to partially be directed toward one crystallographic site over the other. Variable temperature synchrotron XRD data are employed to understand intrinsic thermal expansion. Across the solid solution, no intrinsic NTE is observed at the microscopic level, yet a degree of tunability in the thermal expansion coefficient with Ni substitution is demonstrated. The disparities between the intrinsic and bulk thermal expansion properties suggest that a morphological mechanism may have resulted in NTE in the bulk. 

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