Isotope enrichment is the substitution of a naturally occurring isotopic mixture with a single isotope, in order to reduce isotope scattering of phonons and thereby raise thermal conductivity. The source archive boron arsenide dossier reports a 2025 Advanced Science study claiming that isotope-enriched cubic boron arsenide reaches the highest thermal conductivity yet reported for the material.
Why boron isotopes matter in BAs
Because arsenic exists as a single stable isotope, the isotope effect on thermal conductivity in c-BAs is determined solely by boron. Natural boron (natB) consists of two stable isotopes: 19% ¹⁰B and 81% ¹¹B, giving an average atomic mass of 10.81. Enriching boron to a single isotope removes the mass disorder that scatters phonons.
The 2025 result
The Advanced Science paper "Isotope-Enriched Cubic Boron Arsenide with Ultrahigh Thermal Conductivity" (Jaehoon Kim, Dongwook Lee, Huan Wu, et al.) synthesized high-quality c-¹⁰BAs and c-¹¹BAs crystals using a modified chemical vapor deposition method with a transition-metal catalyst. Crystals were 100–400 µm, semi-transparent reddish, predominantly hexagonal or semi-hexagonal.
Using time-domain thermoreflectance (TDTR) measurements, the authors report a room-temperature thermal conductivity of 1500 W/(m·K) for c-¹¹BAs — described as the highest thermal conductivity for isotope-enriched c-BAs reported so far, and surpassing the previously reported experimental value of 1300 W/(m·K). The paper notes that the experimentally measured values exceeded those calculated by ab initio models.
The contested prior state
The paper's introduction is candid that earlier isotope-enrichment studies had recorded "only minimal differences" in thermal conductivity between isotope-enriched and natural c-BAs, with most experimental results in the range of 1100–1300 W/(m·K) regardless of isotopic composition. The authors suggest those results imply that impurities had a more pronounced influence than isotope composition in those samples, and note that significant variations occur among c-BAs crystals grown by identical methods, even within the same batch, with local defects causing considerable deviations.
This makes the isotope-enrichment improvement an unresolved tension in the literature: the 2025 paper claims a clear improvement, while prior work found little difference. The dossier presents both positions without resolving them.
Related pages
- Boron Arsenide (BAs)
- Ultrahigh Thermal Conductivity in Boron Arsenide
- Antisite Defects in Boron Arsenide
Source notes & attribution
- https://rexresearch.com/BoronArsenide/BoronArsenide.html