High pressure phase equilibria in the Li3N-BN system: In situ studies

Powder diffraction of synchrotron radiation at pressures up to 6.3 GPa and DTA at ambient pressure were used to study phase equilibria in the Li3N-BN system at temperatures up to 1820 K. The construction of the Li3N-BN quasibinary section of the Li-B-N ternary system has been refined. The melting of the high-pressure phase of Li3BN2 has been shown to be of an incongruent nature. The existence of the Li3BN2(O) reversible arrow L + BN peritectic equilibrium at 1620 K and 5.3 GPa has been established. It was shown that this peritectic reaction defines the lowest possible temperature of formation of cubic boron nitride in the Li3N-BN system (1670(+/-)50 K in the 5.3-6.3 GPa range).