For example, naturally occurring boron has two isotopes, approximately 20 percent boron-10 and 80 percent boron-11. Most elements in nature have mixtures of isotopes, Broido explained. The team also studied the related compounds, boron phosphide (BP) and boron arsenide (BAs). 'The study confirms c-BN as one of only a handful of ultrahigh thermal conductivity materials, and shows it to have the largest increase in its thermal conductivity upon isotopic enrichment ever observed,' Broido said. The team overcame these challenges, and the measured thermal conductivity values for the c-BN samples were quite close to the ones they had calculated.

Also, it is difficult to measure the thermal conductivity accurately when the value is high. 'We wanted to determine whether high quality c-BN can in fact be made to observe the large thermal conductivity magnitudes in c-BN, and whether the huge increase in thermal conductivity with isotopic purification predicted from theoretical calculations is measured in the real material,' said Boston College Professor of Physics David Broido, a co-author of the report.Ĭ-BN is particularly challenging to make. Theoreticians had predicted that isotopically pure cubic boron nitride (c-BN), should have extremely high thermal conductivity - second only to crystals made out of carbon, such as diamond. But very few of them have been discovered. Materials with very high thermal conductivity have important technological applications, such as cooling microelectronics. The thermal conductivity of a material conveys how much heat can pass through it when its ends are at different temperatures. An international team of physicists, materials scientists, and mechanical engineers has confirmed the high thermal conductivity predicted in isotopically enriched cubic boron nitride, the researchers report in the advance electronic edition of the journal Science.

Boron 10 and boron 11