Lanthanum zirconate porous ceramics with controllable secondary pores for high-temperature thermal insulation

It was an effective way to tailor the pore structure of porous ceramics to enhance the thermal insulating properties at a large temperature range. In this study, a feasible method combining the particle-stabilized foaming method and the pore-forming agent method was developed to fabricate hierarchically porous lanthanum zirconate (LZO) ceramics with ultra-high porosity (P) and controllable secondary pores. With the increasing pore-forming agent (carbon) to 40 vol%, the total porosity reached 95.79 ± 0.08% with secondary pores of 0.47%. The ratio of secondary pores to cell wall increased from 2.39% to 11.17%. Due to the increase of secondary pore percentage, the thermal conduction path increased and the infrared radiation was scattered. Consequently, the thermal conductivity, k, at room temperature was reduced from 0.082 ± 0.001 W/(m·K) to 0.061 ± 0.002 W/(m·K), and the k at 1200 °C decreased from 0.379 ± 0.011 W/(m·K) to 0.317 ± 0.011 W/(m·K). The results provided a feasible method to prepare porous ceramics with controllable pore structure for thermal insulation application.