Liquid phase sintering of yttrium oxide: The effect of Al2O3 and SiO2 additives

Solid-state sintering of Y2O3 is difficult and requires high-temperature heat treatment or the use of a sintering additive. In this study, liquid-phase sintering was utilized to produce dense Y2O3 bodies with fine-grained microstructure. Al2O3 and SiO2 were added to a commercial nano-Y2O3 powder using aluminum nitrate and
tetraethylorthosilicate (TEOS) as the precursors; the samples were uniaxially pressed at 100 MPa and sintered at 1500 ◦C and 1650 ◦C. The addition of the sintering aids increased the relative density of the samples sintered at lower temperatures; also, the sintering aids suppressed grain growth. The dissolution of Y2O3 into the liquid
phase changes the solid-liquid interfacial energy resulting in the formation of isolated yttrium-silicate/yttriumaluminate grains and accounts for the suppression of the growth of yttria grains.