Conventional versus additive manufacturing in the structural performance of dense alumina-zirconia ceramics: 20 years of research, challenges and future perspectives

The current need to develop Additive Manufacturing (AM) processes capable of producing defect-free, fullydense functional ceramics could benefit from the knowledge consolidated throughout the years in conventional processing. This review provides an up-to-date status of AM fabrication of dense alumina, zirconia and their composites, in comparison with reference values published during 20 years of research on powder pressing and colloidal-based technologies. A systematic literature search on conventional methods and AM selected 1706 papers and, after screening, 344 papers included 1313 different experiments reporting relative density and mechanical properties (flexural strength, elastic modulus, hardness and fracture toughness) of the final ceramics. The associations between experimental processing conditions, densification and, subsequently, mechanical performance were evaluated in powder- and suspension-based technologies. The research evolution in the fabrication of these ceramics over the last two decades is also summarized, highlighting the most used AM technologies for each material and the place of functional ceramics in recent and future market perspectives. Furthermore, future insights in the fabrication of functional ceramics are identified, to guide researchers and commercial players in drawing scientific and industrial novelties for developing new business strategies, key decision-making and road mapping to make the AM market of functional ceramics a reality.