Microstructure and properties of highly porous Y2SiO5 ceramics produced by a new water-based freeze casting

This study introduced a new structural/functional porous yttrium silicate (Y2SiO5) ceramic, which was prepared using a water-based freeze-casting technique. Moreover, the effects of sintering temperature on the microstructure, compressive strength, thermal conductivity, and dielectric properties of porous Y2SiO5 ceramics were investigated. The microstructure consisting of 3-D interconnected pores were created using the freezing process, and the formation mechanism was discussed. The microstructure observation indicated an increase in the sintering temperature from 1250 °C to 1450 °C and a decrease in porosity from 71% to 62%. In addition, the pore channel size decreased from 50 μm to 25 μm, but the average grain size increased from 1.0 μm to 3.0 μm. Consequently, the compressive strength, thermal conductivity, and dielectric constant of the porous Y2SiO5 ceramics increased from 3.34 MPa to 16.51 MPa, from 0.07 W/m K to 0.22 W/m K, and from 1.89 to 2.22, respectively. Porous Y2SiO5 ceramics with such properties can be applied to ultra-high temperature broadband radome structures and thermal insulators.