Effect of talc powder on properties of Y₂O₃-based ceramics

The rapid advancement of superalloy melting technology has increased the demands on crucible materials. Y₂O₃ is a promising candidate for nickel-based superalloy melting due to its outstanding high-temperature stability and non-wetting behavior with various alloys. However, its poor sintering performance limits its development. High-density Y₂O₃ ceramics were successfully prepared via pressureless sintering at 1600 °C in a carbon-embedded atmosphere with talc powder as an additive. The resulting ceramics achieved optimal properties, including a bulk density of 4.27 g cm^-3, apparent porosity of 1.1%, and cold compressive strength of 311.27 MPa. The talc powder introduced a liquid phase during sintering, which accelerated mass transfer and promoted grain growth and densification. During cooling, this liquid phase remained at the grain boundaries and acted as an intergranular bonding agent, strengthening grain cohesion. Nevertheless, excessive liquid phase hindered grain growth, negatively affecting sintering. Additionally, the extremely low porosity and the formation of the Mg₂SiO₄ phase reduced the residual strength retention ratio of the Y₂O₃ ceramic after thermal shock.