Enhanced thermal insulation and mechanical properties of Y-α-SiAlON porous ceramics with Sr doping

α-SiAlON is a potential wave-transmittance material for radome materials, yet the comprehensive properties need to be improved. In this study, a series of Sr_xY_0.5-xSi_{12-(m + n)} Al_{m +n}O_nN_16-n (x = 0.02, 0.04, 0.06, and 0.08) porous ceramics with porosities ranging from 44.15% to 58.62% were synthesized via tert-butanol gel-casting. The real part of the permittivity of porous ceramics was in the range of 3.13–4.18 (8.2–12.4 GHz) with over 70% wave transmittance in the thickness range of 5.5–9.5 mm. The thermal conductivity and flexural strength of porous ceramics were in the ranges of 1.063–1.703 W/(m·K) and 52.67–106.33 MPa, respectively. Compared with Y-α-SiAlON porous ceramics, the thermal insulation and mechanical properties of Sr/Y-α-SiAlON porous ceramics are improved without deteriorating wave transmittance properties. The results show that Sr/Y-α-SiAlON porous ceramics have the potential to be wave-transmittance materials by adjusting the wave transmittance, thermal insulation, and mechanical properties of α-SiAlON.