Fabrication and microstructure characterization of W-La₂O₃-Y₂O₃ composites by spark plasma sintering and hot isostatic pressing

The fabrication of dense W composites dispersed with La₂O₃ and Y₂O₃ nanoparticles had been attempted by combining a spark plasma sintering with post hot isostatic pressing. W powders dispersed with La₂O₃ particles were prepared by ultrasonic spray pyrolysis using ammonium metatungstate hydrate and lanthanum nitrate, and then yttrium nitrate was added to finally synthesize W-La₂O₃-Y₂O₃ composite powders. TEM analysis revealed that La₂O₃ and Y₂O₃ nanoparticles were uniformly distributed in the synthesized W composite powders. The relative density of composites prepared by spark plasma sintering was found to increase with increasing amounts of oxide particles and also with post hot isostatic pressing. The densified composites containing 1 wt% each of La₂O₃ and Y₂O₃ particles showed smaller grain size and higher hardness than that containing 0.5 wt% each of oxide particles. Changes in relative density, grain size and hardness with the oxide content are discussed considering the observed microstructural features and the role of oxide particles in mass transport and grain growth.