Cubic-to-rhombohedral transformation in boron nitride induced by laser heating:In situRaman-spectroscopy studies

In situ Raman-spectroscopy studies were carried out on Ar-ion-laser-heated cubic boron nitride (cBN). Phase identification and temperature measurements were performed on micron-size particles and a pressure-compacted free-standing thin film of cBN. In both cases, cBN was shown to transform to the rhombohedral phase (rBN) above 1795±80 K with characteristic Raman peaks at 790 and 1366 ${\mathrm{cm}}^{\mathrm{-}1}$ at ambient conditions. The cBN-to-rBN transformation proceeds with a characteristic time of 1 s. The temperature variation of Raman modes of rBN were measured to 1800 K.