In order to investigate the phase transformation of boron nitride nanoparticles in solvothermal solutions, BN was synthesized by reacting BCl3 and Li3N in pyridine under a rather mild condition. During the synthesis process, the influences of reaction temperature, pressure and duration were intensively investigated, finding that the earliest BN phase appearing in the solution was aBN, in which B and N atoms arranged in a random way. After that, the order degree of B and N atom arrangement was improved gradually with increasing the temperature and pressure and prolonging the reaction duration, thus tBN and hBN formed. Besides, the content of tBN increased at first when the temperature and pressure increased, followed by the increase of hBN and the decrease of tBN. This result reveals that a phase transformation of aBN®tBN®hBN happened in the reaction solution under such a circumstance.

Key words: pyridine-thermal synthesis, boron nitride, phase transformation