Thermal Flash Annealing Stabilizes the Tetragonal Phase in Zirconia Microarchitectures as Revealed by Europium Optical Probing
Cristian Rosero-Arias, Francisco Ruiz-Zepeda, Martin Drobek, Marie-Alix Pizzoccaro-Zilamy, Rogelio Salazar-Avila, Carolina Mendoza, Arturo Ponce, Alan Aguirre-Soto, Han Gardeniers, Arturo Susarrey-ArceAbstract
Controlling polymorphism in ceramic microarchitectures is essential for linking processing, structure, and function yet remains difficult for ceramics produced by two-photon lithography (TPL). During thermal conversion, crystallite growth typically promotes the thermodynamically stable monoclinic (m) phase, restricting access to tetragonal (t)-ZrO2. Here, we show that infrared (IR) flash annealing stabilizes t-ZrO2 microarchitectures over a broad 600–1000 °C treatment window. Rapid IR heating (20 °C s–1) limits crystallite growth and suppresses the t-to-m transformation commonly observed near 750 °C under slower annealing. Scanning transmission electron microscopy (STEM) confirms crystallite-size-dependent t-stabilization during rapid IR heating, while Europium (Eu3+) serves as an embedded optical probe of local symmetry, providing distinct photoluminescence signatures without destructive preparation. Flash thermal processing controls polymorphism, while luminescent symmetry probing enables its non-destructive diagnosis in 3D ceramic microarchitectures, providing a transferable approach for studying phase evolution in lanthanide-doped ceramics.