One-step reactive sintering of La2Ti2O7 from La2O3–TiO2: Spark plasma sintering vs pressureless consolidation and interpretable machine-learning density prediction

La 2 Ti 2 O 7 (LTO) is a layered perovskite significant for high-temperature dielectric and ferroelectric applications. Traditional methods for achieving dense ceramics involve a two-step process, but we present a one-step reactive sintering approach using mixed La 2 O 3 –TiO 2 precursors to directly form dense, single-phase LTO. We compare spark plasma sintering (SPS) and pressureless sintering (PS) at 1000–1200 °C. X-ray diffraction analysis confirms monoclinic LTO formation at high temperatures, while low-temperature PS shows limited consolidation. SPS achieves 92.47% relative density at 1200 °C in 15 min, whereas PS reaches 86.93% after 120 min with more porosity. To identify the dominant densification factors, structural and microstructural descriptors derived from X-ray diffraction and scanning electron microscope were integrated into regression models. Among the evaluated models, partial least squares regression provided the best predictive performance. Interpretable machine-learning analysis revealed that density is governed primarily by pore-network descriptors, specifically Porosity × STD, Phase Count, Porosity (%), and STD/Size, rather than by nominal processing variables alone, whereas nominal processing variables primarily influence microstructural evolution. These results demonstrate that calcination-free reactive SPS is an efficient route for producing dense LTO and establish a descriptor-based framework for understanding and optimizing reactive ceramic sintering.