Structural Evolution under High Pressure and at High Temperature of a β’-Sialon Phase

Abstract

The structure of a β’-sialon phase of general formula Si_6–zAl_zO_zN_8–z (with z = 2·13) was studied by time-of-flight neutron diffraction.

The sample contained more than one phase and at the beginning this was thought to be Si₃N₄. In fact, due to the accuracy of the time of flight technique it was found that it was another β’-sialon phase richer in nitrogen.

After a short description of the time-of-flight neutron diffraction and of the jointed profile analysis technique, the structure is presented. Its evolution under high pressure and at high temperature is given in terms of motion of the [Si(Al), N(O)]₄ tetrahedra. This motion is compared with the motion in other nitrides or oxynitrides such as Si₃N₄, AIN and Si₂N₂O of the SiN₄ and SiON₃ tetrahedra.