Circumventing Thermodynamic Constraints in Nucleation-Controlled Crystallization of Al₂TiO₅-Based Chemical Vapor Deposition Coatings

Nucleation is a fundamental part in most syntheses of ceramic materials. Yet, few techniques enable control this step, which would offer possibilities to attain full-scale kinetic selectivity the reach novel compounds with unique properties. Herein, we present nucleation-controlled crystallization pathway synthesize coatings aluminum titanate (Al2TiO5)─renowned for its low-to-negative thermal expansion─at significantly reduced temperatures than conventional solid-state techniques. Based on study using situ X-ray diffraction, detailed mechanistic insights into process and phase evolutions within Al–Ti–O system are obtained. The lowest activation energies given when Al–Ti ratio close-to-stoichiometric or Ti-enriched. Along these compositions’ similar kinetics at earliest stages transformation, joint nucleation behavior discovered, revealing elemental role titanium nucleating main Al2TiO5 phase. classical theory, deduce significant influence configurational entropy (Sconfig) occurs domain. Finally, peculiar transition features observed Al-enriched regime during annealing intermediate temperatures, whose causes ascribed presence secondary events structural relaxations amorphous matrixes crystallizing.