Gas pressure sintering of BN/Si3N4 wave-transparent material with Y2O3-MgO nanopowders addition

BN/Si3N4 ceramics performed as wave-transparent material in spacecraft were fabricated with boron nitride powders, silicon nitride powders and Y2O3-MgO nanopowders by gas pressure sintering at 1700 degrees C under 6 MPa in N-2 atmosphere. The effects of Y2O3-MgO nanopowders on densification, phase evolution, microstructure and mechanical properties of BN/Si3N4 material were investigated. The addition of Y2O3-MgO nanopowders was found beneficial to the mechanical properties of BN/Si3N4 composites. The BN/Si3N4 ceramics with 8 wt% Y2O3-MgO nanopowders showed a relative density of 80.2%, combining a fracture toughness of 4.6 MPa m(1/2) with an acceptable flexural strength of 396.5 MPa. Crown Copyright (C) 2014 Published by Elsevier Ltd and Techna Group S.r.l.