Grain refinement in ceramic additive manufacturing: Mechanisms, strategies and performance implications

Ceramic additive manufacturing (AM) has advanced considerably over the past few decades, enabling the reliable fabrication of dense components with complex geometries. As the field shifts from densification toward performance-oriented microstructural design, grain refinement has become central to reducing defects and improving mechanical performance. However, a systematic review dedicated to this topic is still lacking. This work therefore reviews grain refinement with primary emphasis on currently dominant indirect AM routes, while also discussing direct melting-based routes as emerging approaches. It first analyzes route-dependent microstructure formation mechanisms to establish a basis for microstructural control, and then critically evaluates the major refinement strategies, including compositional design, external-field assistance and post-processing, with emphasis on their effectiveness and limitations. Grain size-property relationships, particularly those related to mechanical performance, are also discussed, and key knowledge gaps and research priorities are identified to guide future progress in ceramic AM for microstructural control and performance optimization.