Giant Functional Properties in Porous Electroceramics through Additive Manufacturing of Capillary Suspensions

Hierarchical structuring of functional ceramics has long been recognized as a strategy to enhance material performance. Prior research has shown that structural design can influence dielectric and electromechanical properties. However, achieving precise control over porosity and architecture remains a challenge. Traditional methods often limit the complexity of the resulting structures. This gap motivated the development of new fabrication techniques. Additive manufacturing offers the potential to create tailored geometries. Yet, few studies have combined capillary suspension inks with 3D printing for functional ceramics. The need for high porosity and connectivity in barium titanate has not been fully addressed. This work introduces a novel approach to overcome these limitations.

This study aimed to develop a method for creating highly porous, hierarchically structured barium titanate ceramics. The goal was to achieve 3-3 connectivity through direct ink writing. The researchers sought to combine micro- and meso-scale porosity in a single structure. They explored the use of capillary suspension-type inks for this purpose. The motivation was to enhance dielectric and electromechanical coupling. The team wanted to demonstrate the feasibility of additive manufacturing for this application. They also aimed to achieve porosities exceeding 60% in the final structures. The ultimate objective was to improve the energy harvesting performance of barium titanate.

The researchers used direct ink writing to fabricate barium titanate structures. They formulated capillary suspension-type inks with a ternary solid/fluid/fluid composition. The inks relied on capillary forces to self-organize particle networks. The printed structures featured struts with a pore size of approximately 1 μm. The mesostructure of the printed parts had a scale of about 100 μm. The ink's flow properties enabled high strut-to-pore size ratios. The printed parts were sintered to finalize the porous architecture. The resulting log-pile structures had closed bottom and top layers.

The printed structures achieved total porosities greater than 60%. The combination of micro- and meso-scale porosity was confirmed through imaging. The strut porosity was approximately 1 μm in size. The mesostructure had a scale of around 100 μm. The 3-3 connectivity was successfully realized in the printed parts. The energy harvesting figure of merit FOM₃₃ exceeded previous records. The FOM₃₃ was more than four times higher than any prior data for barium titanate. The results demonstrated the potential of the method for functional ceramics.

The authors demonstrated that additive manufacturing of capillary suspensions can produce complex 3D structures. The method allows for the creation of highly porous barium titanate ceramics. The combination of micro- and meso-scale porosity enhances dielectric properties. The 3-3 connectivity contributes to improved electromechanical coupling. The sintering process plays a key role in finalizing the structure. The FOM₃₃ values achieved were unprecedented for this material. The approach opens new possibilities for energy harvesting and other applications. The results suggest that the method is suitable for a range of functional ceramics.