Phase transformation of boron nitride under hypothermal conditions

Phase transformation among different boron nitride (BN) phases in hydrothermal solution was investigated. It was found that hexagonal boron nitride (hBN) firstly formed in the solution at relatively low temperature (i.e., 220 °C). After that, a spot of hBN began to transform into wurtzite boron nitride (wBN) and cubic boron nitride (cBN) at 230 °C. More and more hBN converted into wBN and cBN with the increase in temperature, and this transformation process completed at 300 °C. In this paper, we have explained the mechanism of the above phase transformation by using a reported “puckering mechanism”.