In situ construction of one-dimensional structures induced by Ba doping in Al₂O₃-TiO₂ ceramics derived from quenched powders

In this work, we propose a strategy for in situ construction of rod-like grains in Al₂O₃-TiO₂ ceramics through Ba doping. Ba-doped Al₂O₃-13 wt% TiO₂ composite powder was initially synthesized using combustion synthesis-air atomization, where feedstocks were melted by the Al-O₂ combustion reaction and subsequently atomized and rapidly cooled in air, producing quenched powders rich in metastable phases. Upon heat treatment at 1100℃, the metastable phases transformed into stable forms, accompanied by phase separation and solid solution precipitation. Notably, Ba doping induced the formation of rod-like hollandite grains with preferential growth along the [001] direction. Bulk ceramics were prepared through pressureless sintering, and the sample sintered at 1350℃ exhibited a hardness of 14.14±0.61 GPa and a fracture toughness of 5.17±0.49 MPa∙m^1/2. The toughening behavior of rod-like grains, including crack deflection and pull-out/bridging effects, was observed. This study provides insights into the evolution of quenched oxides and the design of ceramic microstructures.