Observing and Modeling the Sequential Pairwise Reactions that Drive Solid- State Ceramic Synthesis

Abstract

Solid- state synthesis from powder precursors is the primary processing route to advanced multicomponent ceramic materials. Designing reaction conditions and precursors for ceramic synthesis can be a laborious, trial- and- error process, as heterogeneous mixtures of precursors often evolve through a complicated series of reaction intermediates. Here, ab initio thermodynamics is used to model which pair of precursors has the most reactive interface, enabling the understanding and anticipation of which non- equilibrium intermediates form in the early stages of a solid- state reaction. In situ X- ray diffraction and in situ electron microscopy are then used to observe how these initial intermediates influence phase evolution in the synthesis of the classic high- temperature superconductor YBa2Cu3O6+x (YBCO). The model developed herein rationalizes how the replacement of the traditional BaCO3 precursor with BaO2 redirects phase evolution through a low- temperature eutectic melt, facilitating the formation of YBCO in 30 min instead of 12+ h. Precursor selection plays an important role in tuning the thermodynamics of interfacial reactions and emerges as an important design parameter in planning kinetically favorable synthesis pathways to complex ceramic materials.Multicomponent ceramics are often synthesized in a - black- box- reactor, with little understanding of how multiple precursors evolve into a target material. Ab initio modeling and in situ observations are used to interrogate the phase evolution of YBa2Cu3O6+x (YBCO), highlighting the critical role of precursor selection in designing kinetically favorable synthesis pathways.