Preparation and properties of ZrO₂-strengthened porous mullite insulation materials using Y₂O₃ additive

ZrO₂-strengthened porous mullite insulation materials were prepared by foaming technology utilizing ZrSiO₄ and Al₂O₃ as primary materials and Y₂O₃ as an additive. The effects of Y₂O₃ contents on the phase composition, microstructure, mechanical properties, and heat conductivity of the porous mullite insulation materials were investigated. A suitable Y₂O₃ content could promote phase transition of monoclinic ZrO₂ (m-ZrO₂) to tetragonal ZrO₂ (t-ZrO₂), reduce pore size, and improve the strengths of as-prepared specimens. The cold crushing strength and bending strength of as-prepared specimens with a 119 µm spherical pore size using 6 wt.% Y₂O₃ were 35.2 and 13.0 MPa, respectively, with a heat conductivity being only 0.248 W/(m K).