Effects of Sintering Method and Sintering Temperature on the Microstructure and Properties of Porous Y2SiO5

Porous Y2SiO5 ceramic is a promising high-temperature thermal insulator in harsh environment. However, all the published relevant works faced serious problems, such as severe linear shrinkage, low porosity and low strength. In this study, porous Y2SiO5 ceramic with low sintering shrinkage and high porosity was successfully prepared by foam-gelcasting method using gelatin as the gelling agent. The effects of sintering methods, including in situ reaction sintering and direct sintering, and sintering temperatures on the phase composition, microstructure, shrinkage, porosity, and compressive strength of porous Y2SiO5 were investigated. Compared with samples fabricated by direct sintering, porous Y2SiO5 ceramic prepared via in situ reaction sintering method has the merits of the low linear shrinkage of 1.0%-4.7%, low bulk density of 0.79-0.88 g/cm3, high porosity of 82.1%-80.1%, and high strength of 3.54-8.03 MPa, when the sintering temperatures increase from 1350 to 1550 °C. Porous Y2SiO5 has unique multiple pore structures, especially containing the interconnected small pores in skeleton. The thermal conductivity of porous Y2SiO5 is very low, which is 0.228 W/(m⋅K) for the sample with a porosity of 79.6%. This work reports an optimal processing method of highly porous Y2SiO5 with the potential application as high-temperature thermal insulation material.