High-temperature lithium transport and phase evolution in amorphous Al₂O₃ exposed to lead–lithium

Ceramic materials exposed to lithium-containing environments are of interest for applications including solid-state electrolytes, electrochemical storage, and fusion reactor systems. In fusion blankets, ceramic coatings deposited on steel substrates must withstand high-temperature operation in contact with lithium-containing coolants while providing chemical stability, electrical insulation, and corrosion protection. This work investigates lithium transport, phase evolution, and chemical stability in ceramic coatings exposed to liquid lead-lithium environments. Amorphous Al₂O₃ coatings deposited by pulsed laser deposition (PLD) on EUROFER97 steel were exposed to static lead-lithium eutectic at 550 °C for up to 7000 h. Coating evolution was investigated by combining X-ray photoelectron spectroscopy (XPS), atom probe tomography (APT), transmission electron microscopy (TEM), and X-ray diffraction analyses with kinetic and thermodynamic modeling. Exposure to lead-lithium induces an amorphous-to-crystalline transition associated with the formation of the lithium-containing ternary phase LiAl₅O₈. Lithium rapidly diffuses into the alumina coating during early exposure stages, reaching a stable bulk concentration of approximately 3–4 at% after less than 1000 h. ... mehrA lithium-enriched region develops at the coating–liquid metal interface, while localized lithium accumulation is also observed near the coating–steel interface. Despite lithium incorporation and partial crystallization, no significant lithium penetration into the EUROFER97 substrate is detected. These findings provide new insights into lithium incorporation mechanisms and phase evolution in ceramic coatings exposed to lithium-containing liquid metals, highlighting the importance of advanced characterization techniques for understanding their long-term behavior.