TY  - JOUR
AU  - Cheng, Shichang
AU  - Yang, Hongbing
AU  - Han, Yao
AU  - Wang, Chang-An
AU  - Dong, Yanhao
PY  - 2026
TI  - Processing strong MgAl2O4 ceramics via zirconia transformation toughening
JO  - Journal of Materiomics
SN  - 2352-8478
VL  - 12
IS  - 5
AB  - The applications of magnesium aluminate spinel (MgAl2O4) ceramics often require optical transparency, suggesting minimal macroscopic flaws otherwise too strong light scattering would make them opaque. Yet the flexural strength typically in 200–350 MPa range is unsatisfactory, suggesting rather large critical flaw size for fracture in brittle materials. Such inconsistency makes MgAl2O4 an interesting system to study ceramic processing, strengthening, and toughening. Here, we reported progress in pressurelessly sintered zirconia toughened MgAl2O4 ceramics with 700 MPa flexural strength, surpassing those reported in the literature by hot pressing and other techniques. The new advance was achieved by colloidal processing and two-step sintering, for improved microstructural control, minimized microscopic defects, uniform two-phase distribution, and suppressed grain growth. We found ZrO2 acts as sintering aid for MgAl2O4, effectively lowering the sintering temperature by 150 ℃. The optimized two-step sintering was conducted first at 1325 ℃ without holding reaching a critical relative density of 93%, and then at 1225 ℃ for 20 h for full densification. The low pressureless sintering temperature of 1225 ℃ plus the two-phase inter-pinning refine the grain size to 184 nm for MgAl2O4 and 155 nm for zirconia, offering microstructural benefits for strengthening. The zirconia grains stabilized by matrix constrain and partial Mg2+ alloying are mostly tetragonal and mechanically transformable, offering active toughening mechanism to reduce flaw sensitivity. The fracture is intra-granular for MgAl2O4 and mixed intra- and inter-granular for zirconia. Our work demonstrates the possibility to further strengthen MgAl2O4 ceramics towards 1 GPa for advanced and new applications.
UR  - https://doi.org/10.1016/j.jmat.2026.101278
DO  - 10.1016/j.jmat.2026.101278