Interlayer bonding in vat photopolymerization additive manufactured ceramics with enhanced mechanical properties

Abstract The performance of vat photopolymerization (VPP) additive manufactured ceramics is critically limited by weak interlayer bonding, which represents a challenge inherent to the layer-by-layer process. However, current research often optimizes stereolithography and sintering as separate stages, overlooking the dynamic evolution of the interlayer. This study introduces a novel paradigm by conceptualizing the interlayer as a dynamic system evolving under photothermal fields. A strategy of cross-process synergistic control, actively interlayer evolution rather than passively reducing defects, was proposed. We systematically investigate key stereolithographic parameters (irradiance, exposure time, and slicing thickness) and sintering protocols, focusing on the collaborative mechanism between photopolymerization dynamics and sintering kinetics in the interlayer. Orthogonal design identifies slicing thickness as the most critical factor. By precisely controlling the ultraviolet (UV) energy input, a controlled incompletely polymerized state is introduced to enhance interlayer bonding via an effective dynamic balance between primary and secondary photopolymerization. Subsequent sintering is tailored to improve the particle packing density at the interlayer. The ZrO2 ceramic achieves a high flexural strength of 425.89±16.01 MPa and a relative density of 97.21%±0.14% after sintering at 1550 °C for 2 h. This work establishes a framework that links process parameters to interlayer evolution and properties, offering both a practical pathway and a novel theoretical perspective for manufacturing high-performance ceramics.