The researchers report TlFe1.6Se2, a layered material in which atomically thin FeSe sheets are periodically embedded inside a bulk host. The concept is to inherit the superior thermoelectric power factor associated with ultrathin FeSe while simultaneously suppressing heat flow in the surrounding crystal.

In their approach, the embedded FeSe layers coexist with ordered iron (Fe) vacancies. These vacancies act as built-in “phonon scatterers.” By disrupting local bonding and creating a complex lattice landscape, the vacancies strongly reduce the mobility of heat-carrying vibrations, lowering lattice thermal conductivity.

Electrical performance improves at the same time. The team finds that Seebeck coefficient values exceed 100 μV K−1 in the Fe-vacancy-ordered phase, delivering a thermoelectric power factor roughly five times larger than in the vacancy-disordered phase. The enhancement is linked to electronic structure changes induced by the vacancy ordering.

A key feature is a reversible temperature-driven transition near 180 °C, where the vacancy arrangement shifts from ordered to disordered. This dynamic behavior further strengthens phonon scattering and pushes thermal conductivity down to about 0.2 W m−1 K−1—at the level of, or lower than, leading thermoelectrics.

The results highlight a “low-dimensional functionality in bulk form” strategy: instead of building devices from films alone, the material embeds the benefits of two-dimensional physics inside a practical bulk crystal. Heavy thallium (Tl) atoms and the complex layered stacking additionally contribute by reducing phonon velocities and increasing scattering.

The publication also suggests broader applicability. Related alkali-intercalated FeSe systems containing potassium, rubidium, or cesium may offer tunable vacancy concentrations, providing a pathway to further optimize thermoelectric performance.

Overall, TlFe1.6Se2 demonstrates that power factor and thermal suppression can be engineered together through structural design—offering a viral, concept-forward blueprint for next-generation waste-heat converters.

Keywords
Thermoelectricity; FeSe; Vacancy ordering; Lattice thermal conductivity; Seebeck coefficient; Power factor; Layered crystals; Phonon scattering

Subject of Research: Not applicable
Article Title: Simultaneous enhancement of power factor and suppression of thermal conductivity in bulk TlFe1.6Se2 via embedded atomically thin FeSe layers
News Publication Date: 30-Apr-2026
Web References: https://pubs.rsc.org/ta/article/14/37/24666/1243050/Simultaneous-enhancement-of-power-factor-and
References: 10.1039/D6TA02075E
Image Credits: Institute of Science Tokyo

Harnessing the power of advanced electron microscopy and scanning thermal probe methodologies, the research team delved into the atomic architecture of the bismuth-antimony-telluride alloy, a paradigmatic thermoelectric material widely employed for its ability to convert waste heat into electrical energy. Their detailed analysis illuminated previously overlooked microstructural phenomena, focusing in particular on the distribution and alignment of edge dislocations—minute defects traditionally considered mere imperfections but now revealed as crucial modulating agents of phonon scattering and thermal resistance.

Conventional wisdom posited that the thermal conductivity of heterogeneous materials was primarily dictated by the nature and scale of their compositional mixing. However, the QUT team’s findings challenge this narrative, demonstrating that the random spatial arrangement of edge dislocations plays a far more pivotal role in impeding heat flow. These dislocations, scattered in disordered orientations throughout the uneven matrix, act as formidable barriers that disrupt the smooth propagation of phonons—the primary heat carriers in non-metallic solids—thus dramatically suppressing thermal conduction.

By systematically comparing samples with varying degrees of compositional ordering, the researchers observed a striking correlation: materials exhibiting greater randomness in the distribution of bismuth- and antimony-rich domains consistently manifested lower thermal conductivity values. This phenomenon cannot be solely attributed to compositional disparity but is intricately linked to the scattering effects induced by the erratic alignments of dislocation lines. The team’s innovative approach to visualizing and quantifying these defects at such an unprecedented resolution has opened an entirely new dimension in materials science.

The implications of this discovery transcend academic curiosity, heralding tangible advancements for industrial applications where thermal management is paramount. From the optimization of thermoelectric generators—devices that convert heat differentials directly into usable electricity—to the enhancement of thermal insulation materials designed to conserve energy in buildings and aerospace technology, the ability to precisely engineer defect landscapes could revolutionize performance metrics and energy efficiencies.

Leading the project, Professor Zhi-Gang Chen highlighted that this newfound understanding not only enriches the fundamental physics of heat transport but also establishes actionable design principles for fabricating materials with tailor-made thermal properties. By manipulating the formation processes and spatial arrangements of edge dislocations, materials scientists can now strategically attenuate thermal conductivity while preserving other crucial mechanical and electrical characteristics, a feat that was elusive under traditional defect engineering paradigms.

First author Siqi Liu emphasized that this structural insight reframes the design philosophy of thermoelectric materials, shifting attention from mere compositional engineering to the orchestration of microstructural inhomogeneities at the nanoscale. “Our work illustrates that it is not just the materials’ composition but the geometric and statistical configuration of their defects that governs thermal behavior,” Liu explained. “This paradigm shift opens a new target for controlling heat flow with atomic precision.”

The study’s success was borne out of the integration of sophisticated experimental techniques capable of probing local chemical and thermal variations with atomic fidelity. Scanning thermal probes mapped heat flow with exquisite spatial resolution, while electron microscopy unveiled the arrangement of various compositional domains and their associated dislocations, enabling a comprehensive correlation between structure and thermal transport phenomena.

Moreover, the findings resonate across a spectrum of scientific disciplines and industries, promising to influence the development of novel materials beyond thermoelectrics. For instance, the ability to modulate heat conduction via controlled defect alignment could inspire breakthroughs in thermal barrier coatings, semiconductor device cooling, and even gas storage materials where thermal management influences storage efficiency and safety.

With the release of their comprehensive research article titled “Alignment of edge dislocations – the reason lying behind composition inhomogeneity induced low thermal conductivity,” published in Nature Communications, the QUT team invites the scientific community to explore the manifold applications and theoretical interpretations of their discovery. This work stands as a testament to the power of combining atomic-scale imaging with thermal characterization to solve complex material science challenges.

Looking forward, the team is committed to extending these insights by experimenting with alternative compounds and synthesis methods to refine control over dislocation patterns. Such endeavors aim to unlock new classes of materials that optimize energy conversion processes, reduce environmental footprints, and enhance the sustainability of future technologies.

In sum, the identification of randomly aligned edge dislocations as a fundamental structural mechanism driving low thermal conductivity reshapes our understanding of heat transport in compositionally inhomogeneous materials. This breakthrough not only enriches scientific knowledge but equips engineers and designers with novel strategies to tune thermal properties, paving the way for innovations that could profoundly impact energy harvesting and thermal management technologies worldwide.

Subject of Research: Not applicable

Article Title: Alignment of edge dislocations – the reason lying behind composition inhomogeneity induced low thermal conductivity

News Publication Date: 5-Nov-2025

Web References:
https://doi.org/10.1038/s41467-025-64749-5

References:
Liu, S., Liu, W-D., Lyu, W., Yue, Y., Gao, H., Li, M., Shi, X-L., Chen, Z-G. (2025). Alignment of edge dislocations – the reason lying behind composition inhomogeneity induced low thermal conductivity. Nature Communications. https://doi.org/10.1038/s41467-025-64749-5

Image Credits: QUT

Keywords

Electricity, Thermoelectricity, Energy

The study centers around the intrinsic ability of BAs to conduct heat, a property quantified by thermal conductivity measured in watts per meter per Kelvin (W/mK). Until recently, diamond has been considered the pinnacle of heat conduction among isotropic materials, boasting exceptional thermal conductivity. Conventional wisdom based on theoretical models, especially those incorporating four-phonon scattering mechanisms, placed an upper limit on BAs’ thermal performance at roughly 1,360 W/mK, prompting skepticism about BAs’ capabilities beyond this figure.

Nevertheless, the University of Houston team, led by Professor Zhifeng Ren of the Department of Physics and director of the Texas Center for Superconductivity, challenged these theoretical ceilings by refining crystal synthesis processes. They hypothesized that imperfections and impurities in previously studied BAs samples were obscuring its true potential. Through meticulous purification of raw arsenic and employing advanced crystal growth techniques, they succeeded in producing near-perfect BAs single crystals exhibiting thermal conductivities exceeding 2,100 W/mK at ambient temperature. This value not only transcends prior experiments but also eclipses the benchmark thermal conductivity of diamond.

This breakthrough bears profound implications for material science and engineering. Thermal conductivity governs how efficiently heat can be extracted or distributed within an electronic device, directly influencing performance reliability and longevity. Silicon, the dominant semiconductor material in the electronics industry, falls short in thermal management, necessitating external cooling solutions. In contrast, BAs emerges as a promising candidate combining superior heat conduction with semiconductor properties, enabling intrinsic thermal regulation in devices.

Furthermore, BAs distinguishes itself with manufacturing advantages. Unlike diamond, which demands extreme conditions like high pressure and temperature for synthesis, BAs can be created through comparatively accessible and cost-effective processes. The material’s wide band gap and high carrier mobility also suggest that it may outperform silicon in electronic applications, potentially revolutionizing the semiconductor market by integrating high thermal conductivity and electronic efficiency into a single, manufacturable material.

The collaborative research effort, involving experts from the University of California at Santa Barbara and Boston College, benefited from diverse expertise encompassing theoretical physics and materials synthesis. Notably, initial theoretical predictions by Boston College physicist David Broido foresaw BAs’s potential for superior heat conduction, but subsequent modeling updates incorporating complex phonon interactions like four-phonon scattering had dampened optimism. The latest experimental data decisively underscore the need to revisit and refine these theoretical models to fully capture BAs’s unique phonon dynamics.

The experiments employed highly sophisticated measurement techniques to precisely quantify thermal conductivity in crystalline samples. By minimizing defect-induced phonon scattering, the team achieved a closer approximation of ideal lattice conditions, revealing BAs’s intrinsic capability. These results necessitate recalibrating computational models that previously constrained expectations, signaling a paradigm shift in understanding phonon transport phenomena in semiconductors with complex lattice structures.

Beyond theoretical importance, this research heralds practical benefits for technology sectors reliant on efficient heat dissipation, such as next-generation cell phones, high-power electronic devices, and data centers. As device architectures shrink and computational loads intensify, managing thermal output becomes paramount. Materials like BAs could radically improve device performance and energy efficiency by inherently managing heat without bulky cooling systems, reducing size, weight, and energy consumption.

Professor Ren emphasizes that this is just the beginning. The team intends to further enhance BAs’s thermal properties by refining material synthesis and investigating phonon transport mechanisms at microscopic scales. The $2.8 million National Science Foundation grant supporting this work facilitates interdisciplinary collaboration among several leading universities, promising accelerated progress toward integrating BAs into practical technologies.

This research also serves as an inspiring reminder that scientific inquiry should remain open to experimental evidence even when it challenges established frameworks. Dr. Ren states, “You shouldn’t let a theory prevent you from discovering something even bigger.” By pushing beyond conventional theoretical boundaries, the team not only invigorates phonon physics research but also paves the way for discovering next-generation materials with extraordinary multifunctional properties.

In conclusion, the University of Houston team’s groundbreaking discovery of exceptional thermal conductivity in boron arsenide thrusts this synthetic material into the spotlight as a contender to surpass diamond’s heat conduction capabilities. With its combination of superior thermal management and semiconducting potential, BAs could become the cornerstone for future electronic devices that demand both heat dissipation and electronic efficiency. Continued research and theoretical refinement will further illuminate BAs’s capabilities, potentially reshaping the landscape of materials science and semiconductor technology in the years to come.

Subject of Research: Thermal Conductivity and Semiconductor Properties of Boron Arsenide Crystals

Article Title: Boron Arsenide Crystals Surpass Diamond in Thermal Conductivity: A New Frontier in Semiconductor Thermal Management

News Publication Date: October 10, 2025

Web References: Materials Today Article

References: University of Houston, Texas Center for Superconductivity; University of California Santa Barbara; Boston College

Image Credits: University of Houston

Keywords

Physics, Materials Science, Experimental Physics, Thermal Conductivity, Thermal Properties, Isotropy, Conductance, Conductivity, Semiconductors, Heat Conduction, Activity Coefficient, Electronics, Energy Storage, Electrical Conductors, Data Storage