Critical role of the in-situ YAG phase for tailoring mechanical and thermal shock resistance properties of SLA 3D-printed MgAl2O4 ceramics

Conventional forming methods for MgAl 2 O 4 (MAS) ceramics struggle to fabricate complex geometries and face the inherent trade-off between densification and grain growth, while SLA-printed MAS have rarely matched the mechanical properties of their conventionally sintered counterparts. This work proposes an integrated strategy that combines stereolithography (SLA) 3D printing, pressureless sintering, and Y 2 O 3 -induced in-situ Y 3 Al 5 O 12 (YAG) phase formation. Unlike conventional doping studies, we systematically quantified the grain-boundary pinning effect using the Smith–Zener model. As the Y 2 O 3 content increased from 2 to 10 wt%, the YAG content correspondingly rose from 3.3 to 18.0 wt%, and the theoretically predicted limiting grain size of MAS first decreased from 48.09 to 8.04 μm, and then increased to 11.81 μm. The variation trend shows good consistency with the experimentally observed grain size evolution. At an optimal Y 2 O 3 content of 4 wt%, the ceramic achieved a high densification (apparent porosity 0.17%, bulk density 3.48 g cm -3 ), a flexural strength of 256.49 MPa, and a critical thermal shock temperature (ΔT c ) of 214.94 °C. The synergy between SLA and in-situ YAG pinning enables the fabrication of complex-shaped, high-strength, thermally stable MAS components, offering new insights for the development of high-performance engineering ceramics.