Abstract
Laser-based sintering offers a rapid route to sinter garnet-type Li7La3Zr2O12 (LLZO) thin films for all-solid-state batteries (ASSBs) while mitigating secondary phase formation associated with slow furnace heating. This study evaluates the influence of copper(II) oxide (CuO) as a laser-absorbing additive and of process temperature on photonic sintering of Al-doped LLZO (Li6.75Al0.25La3Zr2O12, LALZO) films screen-printed onto titanium substrates. LALZO pastes with 0–3 wt.% CuO and 20 mol% Li-excess (LiOH) were deposited, debinded, preheated to 800 °C and irradiated with a 450nm diode laser for 1 s using pyrometer-controlled peak temperatures between 1100 °C and 1500 °C. Optical, microstructural and crystallographic characterization (UV–Vis–NIR, SEM, XRD) quantified absorptance, densification and phase stability. CuO increased absorptance substantially. 2–3 wt.% CuO yielded the most homogeneous densification across the film thickness. Higher pyrometer temperatures (≥1300 °C) reduced microporosity, but localized in-plane shrinkage, trenching and holes were observed, likely driven by LiOH liquefaction and evaporation causing spatially uneven mass transport. XRD showed preservation of cubic LALZO in CuO-doped samples up to ~1500 °C, whereas Li-deficient La2Zr2O7 formed in undoped films at high temperatures. Results demonstrate that tailored optical absorption and controlled thermal profiles enable rapid laser sintering of high-quality LALZO films on metal substrates, highlighting routes to optimize additive distribution, multi-pass processing and inert atmospheres to achieve dense, phase-pure electrolytes for scalable ASSB manufacturing.