Unexpected metastable transition in high superheating state

By high temperature microscopy, we conducted in-situ observation on the evolution of peritectic melting of YBa₂Cu₃O_7−y thin films (denoted as the α phase). As the α phase was highly superheated above a critical temperature, we found that a non-equilibrium phase transition occurred. An unexpected metastable Y₂O₃ phase (denoted as the γ phase), resulted from the decomposition of the α film, nucleated preferentially to the stable phase of Y₂BaCuO₅ (denoted as the β phase). Both high superheating capability of the α film and low interface energy of the γ phase with substrates are responsible for the metastable phase transition in this work.