Formulation-controlled densification enabling near-theoretical density in extrusion-printed ultra-low-temperature Ag₂Mo₂O₇ dielectric ceramics

Extrusion-based additive manufacturing of functional ceramics is often limited by incomplete densification arising from insufficient particle packing, interfilament porosity, and low green density. Here we show that these limitations are not inherent to the process alone but are strongly influenced by a formulation-controlled coupling between rheology, particle packing, and sintering kinetics. By engineering high solid-loading (78 wt%) Ag₂Mo₂O₇ inks with a multimodal particle size distribution and optimized binder-particle interactions, we achieved improved green packing and filament fusion. This enabled densification beyond the typical extrusion-based ceiling of approximately 93% to reach approximately 96% relative density at 470 °C. The improved packing reduced pore connectivity and promoted enhanced densification at ultra-low temperature. The dielectric response followed the expected porosity dependence, with some deviation from classical mixing behaviour. The resulting ceramics exhibited ε r = 13.5 and Q × f = 23,383, approaching conventionally processed counterparts. Together, these results establish a process-structure-property relationship linking rheology, packing, densification, and dielectric response in extrusion-based ceramics and show that near-theoretical density in DIW systems can be achieved through formulation design.