Lead zirconate titanate (PZT) piezoceramics are widely used in sensors, actuators, and energy harvesters because of their intense electromechanical coupling. As device designs shift toward porous structures, curved parts, and lattice architectures, conventional ceramic processing becomes less practical due to the brittleness, tooling limits, and mold cost. Vat photopolymerization (VPP) additive manufacturing can produce high-resolution parts with a good surface quality, yet PZT printing is often limited by poor curing. Pre-sintered PZT powders can absorb and scatter UV light, which reduces curing depth, weakens interlayer bonding, and causes lateral overcuring that blurs feature edges.

To mitigate these issues, this study was to introduce an integrated "inorganic-precursor photopolymerization + solid-state reaction" route. ZrO₂-TiO₂-PbCO₃-based precursors could replace presintered PZT to improve optical penetration and curing stability during VPP. Meanwhile, La₂O₃ served as a multifunctional dopant to favor sharpen printed features via limiting lateral curing spread, promoted densification, refined grains, and tuned tetragonal-rhombohedral coexistence toward an MPB-adjacent state during sintering. This study could provide a practical way to improve both printability and ferroelectric/piezoelectric performance.

Pb_1-xLa_xZr_0.53Ti_0.47O₃(i.e., x=0、0.01、0.02、0.03、0.04、0.05) precursor powders were prepared via stoichiometric mixing of ZrO₂, TiO₂, PbCO₃ and La₂O₃ and subsequent grinding to ensure the homogeneity. The photocurable slurries with 82% solids were formulated by a TMPTA/PEG400/modified epoxy/HDDA resin system (in a mass ratio of 3∶3∶3∶1), TPO photoinitiator (3% relative to resin), and dispersant (2% relative to powders). The VPP printing was conducted at 12 mW·mm^-2 with an exposure for 3.5 s per layer. The printed parts were subjected to a staged debinding-calcination-sintering, including debinding in N₂ to 350 ℃ for 2 h and 600 ℃ for 2 h under slow heating to mitigate cracking, followed by air burnout/calcination with holds at 600 ℃ and 850 ℃ and final sintering at 1270 ℃ for 2 h. Silver electrodes were screen-printed, and the samples were poled in an oil bath under 3 kV·mm^-1 at 140 ℃ for 15 min. The curing depth and lateral linewidth were quantified via the Beer-Lambert and Gaussian beam fitting. The density/porosity, scanning electron microscopy (SEM) images, X-ray diffraction (XRD) patterns (rietveld refinement), P-E loops, dielectric spectroscopy, d₃₃, and the relaxor diffuseness parameter γ were employed to establish the process-structure-property relationships.

Once presintered PZT powders are replaced by inorganic precursors, the most immediate change appears in curing robustness. Under identical exposure conditions, the single-layer curing thickness increases from 25 μm to 80-85 μm, while the optical penetration depth D_p increases from 9.94 μm to 28-30 μm. With much weaker attenuation in the curing band, the chronic issues of insufficient through-thickness curing and limited interlayer bonding are substantially relieved. A stronger curing does not occur at the cost of poorer fidelity. Lateral broadening becomes easier to restrain. The effective beam half-width w_o decreases from 44 μm in a conventional slurry to 15.0 μm in the precursor system, and further decreases to 13.7 μm after La₂O₃ addition, making the linewidth less sensitive to exposure energy and reducing overcuring-driven edge blurring.

La₂O₃ affects printing and sintering, but its sintering benefit appears only within a limited range. The densification improves as La₂O₃ increases, and then declines as the dopant is excessive. The relative density increases from 94.1 to 99.8% and decreases to 97.6% when La₂O₃ exceeds 3%. In parallel, La₂O₃ strongly refines the microstructure, keeping grains with the sizes of 1.27-2.30 μm, while undoped PZT reaches 8-10 μm under the same conditions, indicating a suppressed abnormal grain growth. The Rietveld refinement shows a single perovskite phase for all the compositions, with MPB-type tetragonal-rhombohedral coexistence. The rhombohedral fraction increases to t 22.4% as x = 0.03 (tetragonal of 77.6%) and then decreases at a higher x, indicating an optimal coexistence as x = 0.03.

The electrical properties follow the same peak behavior. The undoped ceramics show low P_r (i.e., 4.07-4.31 μC·cm^-2) and E_c of 0.78 kV·mm^-1, whereas La doping boosts P_r to 32.87 μC·cm^-2 and E_c to 1.18 kV·mm^-1 as x = 0.03. The dielectric response remains stable from 10² to 10⁵ Hz, with ε_r≈(3.0-3.3) × 10³ and tanδ≈0.03-0.05. The piezoelectric coefficient d₃₃ increases from 205 to 350.6 pC·N^-1 as x = 0.03, then decreaes at a higher x. The relaxor behavior strengthens as well, with γ rising from 1.33 to 1.85 as x = 0.03 (1.86 as x = 0.05). The PFM and TEM images indicate that a moderate La₂O₃ enhances domain switching, while an excess La₂O₃ increases disorder and random-field effects, weakening ferroelectric order and reducing P_r, ε_r, and d₃₃ beyond the optimum.

This work combined precursor-assisted VPP printing with solid-state reaction sintering to improve curing stability, dimensional accuracy, and electromechanical performance in PLZT. The precursor increased curing depth, La₂O₃ limited lateral curing, and the dopant refined grains and supported MPB-adjacent phase coexistence during sintering. The overall performance became optimum as x = 0.03, where P_r, d₃₃, and ε_r increased, while dielectric loss was low, although the more relaxor-like behavior indicated a trade-off between higher response and greater disorder.