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1. Intrinsic Thermal Transport Properties of ZrB ₂ From Room Temperature to Melting Point

   https://doi.org/10.1002/rar2.70315  

   Lee, Yeojin; Xu, Qihao; Jang, Hyejin; Feng, Tianli (May 2026, Rare Metals)

   ABSTRACT Zirconium diboride (ZrB₂) is a promising material for extreme‐environment applications, yet its intrinsic high‐temperature thermophysical behavior remains uncertain: Experiments are highly sensitive to processing conditions, simulations omit key mechanisms, and both rarely reach ultrahigh temperatures. Here, we predict the thermal conductivity (κ), heat capacity, and thermal expansion of ZrB₂from 300 to 3500 K using first principles, explicitly incorporating phonon and electron transport, high‐order phonon scattering, and temperature‐dependent force constants. We estimate that the intrinsic room‐temperature polycrystallineκis ∼169 W m⁻¹ K⁻¹, exceeding the highest experimental value (∼141 W m⁻¹ K⁻¹) limited by microstructural defects, and decreases monotonically to 64.5 W m⁻¹ K⁻¹at 3500 K. Remarkably, this magnitude rivals that of the most refractory metal, tungsten, whereas ZrB₂'s density is three times lower, underscoring its potential for lightweight thermal management. Importantly, electrons dominate heat transport across the entire temperature range, carrying ∼61% ofκat 300 K and ∼91% at 3500 K, indicating that previous research focused solely on phonon engineering may have overlooked the governing role of electronic conduction. The Lorenz number varies non‐monotonically with temperature, deviating significantly from the Sommerfeld valueL₀, indicating that the common assumption of constantL₀may lead to inaccurate thermal–electrical correlations. Phonons dominate heat capacity, though electronic contributions become notable above 1300 K (≈6% at 3500 K). For phonon transport, heat is primarily carried by acoustic modes (≈89% at 300 K) and limited by three‐phonon and electron‐phonon scattering. Counter‐intuitively, four‐phonon scattering is negligible at room temperature, despite the large acoustic–optical gap, because broad optical bands preserve key three‐phonon channels, though the four‐phonon scattering becomes significant at highT. Interestingly, isotopic purification would raise phonon thermal conductivity by ∼23%, whereas temperature‐dependent force constants increase it by 28% at room temperature. Finally, compared with related systems, ZrB₂exhibits nearly twice the thermal conductivity of ZrC at room temperature, mainly because of its significantly higher electronic contribution while maintaining a higher phonon component despite its more complex structure. Althoughκfor ZrB₂decreases with temperature, whereas that of ZrC rises, ZrB₂remains superior across the entire temperature range. This work clarifies the intrinsic thermal transport physics of ZrB₂and highlights its exceptional potential for high‐temperature thermal‐management and aerospace applications. 

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2. Enhanced magnon thermal transport in yttrium-doped spin ladder compounds Sr14−xYxCu24O41

   https://doi.org/10.1063/5.0214897  

   Li, Shuchen; Guo, Shucheng; Wang, Yitian; Li, Hongze; Xu, Youming; Carta, Veronica; Zhou, Jianshi; Chen, Xi (July 2024, Journal of Applied Physics)

   Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound Sr14Cu24O41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline Sr14−xYxCu24O41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19Wm−1K−1, which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. 

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3. Defects vibrations engineering for enhancing interfacial thermal transport in polymer composites

   https://doi.org/10.1126/sciadv.adp6516  

   Zhou, Yijie; Ciarla, Robert; Boonkird, Artittaya; Raza, Saqlain; Nguyen, Thanh; Zhou, Jiawei; Osti, Naresh C; Mamontov, Eugene; Jiang, Zhang; Zuo, Xiaobing; et al (January 2025, Science Advances)

   To push upper boundaries of thermal conductivity in polymer composites, understanding of thermal transport mechanisms is crucial. Despite extensive simulations, systematic experimental investigation on thermal transport in polymer composites is limited. To better understand thermal transport processes, we design polymer composites with perfect fillers (graphite) and defective fillers (graphite oxide), using polyvinyl alcohol (PVA) as a matrix model. Measured thermal conductivities of ~1.38 ± 0.22 W m⁻¹K⁻¹in PVA/defective filler composites is higher than those of ~0.86 ± 0.21 W m⁻¹K⁻¹in PVA/perfect filler composites, while measured thermal conductivities in defective fillers are lower than those of perfect fillers. We identify how thermal transport occurs across heterogeneous interfaces. Thermal transport measurements, neutron scattering, quantum mechanical modeling, and molecular dynamics simulations reveal that vibrational coupling between PVA and defective fillers at PVA/filler interfaces enhances thermal conductivity, suggesting that defects in polymer composites improve thermal transport by promoting this vibrational coupling. 

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4. Pushing the Limits of Heat Conduction in Covalent Organic Frameworks Through High‐Throughput Screening of Their Thermal Conductivity

   https://doi.org/10.1002/smll.202401702  

   Thakur, Sandip; Giri, Ashutosh (April 2024, Small)

   Abstract Tailor‐made materials featuring large tunability in their thermal transport properties are highly sought‐after for diverse applications. However, achieving `user‐defined’ thermal transport in a single class of material system with tunability across a wide range of thermal conductivity values requires a thorough understanding of the structure‐property relationships, which has proven to be challenging. Herein, large‐scale computational screening of covalent organic frameworks (COFs) for thermal conductivity is performed, providing a comprehensive understanding of their structure‐property relationships by leveraging systematic atomistic simulations of 10,750 COFs with 651 distinct organic linkers. Through the data‐driven approach, it is shown that by strategic modulation of their chemical and structural features, the thermal conductivity can be tuned from ultralow (≈0.02 W m⁻¹K⁻¹) to exceptionally high (≈50 W m⁻¹K⁻¹) values. It is revealed that achieving high thermal conductivity in COFs requires their assembly through carbon–carbon linkages with densities greater than 500 kg m⁻³, nominal void fractions (in the range of ≈0.6–0.9) and highly aligned polymeric chains along the heat flow direction. Following these criteria, it is shown that these flexible polymeric materials can possess exceptionally high thermal conductivities, on par with several fully dense inorganic materials. As such, the work reveals that COFs mark a new regime of materials design that combines high thermal conductivities with low densities. 

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5. Origins of ultralow thermal conductivity in 1-2-1-4 quaternary selenides

   https://doi.org/10.1039/c8ta09660k  

   Kuo, Jimmy Jiahong; Aydemir, Umut; Pöhls, Jan-Hendrik; Zhou, Fei; Yu, Guodong; Faghaninia, Alireza; Ricci, Francesco; White, Mary Anne; Rignanese, Gian-Marco; Hautier, Geoffroy; et al (February 2019, Journal of Materials Chemistry A)

   Engineering the thermal properties in solids is important for both fundamental physics ( e.g. electric and phonon transport) and device applications ( e.g. thermal insulating coating, thermoelectrics). In this paper, we report low thermal transport properties of four selenide compounds (BaAg 2 SnSe 4 , BaCu 2 GeSe 4 , BaCu 2 SnSe 4 and SrCu 2 GeSe 4 ) with experimentally-measured thermal conductivity as low as 0.31 ± 0.03 W m −1 K −1 at 673 K for BaAg 2 SnSe 4 . Density functional theory calculations predict κ < 0.3 W m −1 K −1 for BaAg 2 SnSe 4 due to scattering from weakly-bonded Ag–Ag dimers. Defect calculations suggest that achieving high hole doping levels in these materials could be challenging due to monovalent ( e.g. , Ag) interstitials acting as hole killers, resulting in overall low electrical conductivity in these compounds. 

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