PerspectiveThermal Conductivity

Ultrahigh thermal conductivity confirmed in boron arsenide

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Science  10 Aug 2018:
Vol. 361, Issue 6402, pp. 549-550
DOI: 10.1126/science.aau4793

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Few materials possess ultrahigh thermal conductivity κ at room temperature, defined here as exceeding that of copper (κCu ≈ 400 W/m·K), yet such materials are vital for dissipating the heat loads from modern electronics (see the figure). Diamond is the highest-κ bulk material known, with κDiamond as large as 2300 W/m·K, but it is costly to synthesize in sufficient quality and quantity, which limits its impact on applications. On the basis of widely accepted phenomenological theory (1), for decades boron arsenide (BAs) was expected to have an unremarkable κBAs of 200 W/m·K, although this value was never measured. In 2013, a stunning prediction was made that κBAs might be 10 times as high and approach κDiamond (2). Testing such predictions (2, 3) required BAs crystals of unprecedented quality, which launched a flurry of experimental efforts. Reports by Kang et al. (4) on page 575, Tian et al. (5) on page 582, and Li et al. (6) on page 579 of this issue describe the synthesis of small yet superb crystals of BAs and the measurement of κBAs values of ∼1100 W/m·K. These results verify the essence of the predictions (2, 3) and earn BAs long-overdue recognition as an ultrahigh-κ material.