Synthesis and Characterization of High-Entropy Dawsonite-Type Structures.

ABSTRACT

High-entropy hydroxides are an emerging subcategory of high-entropy materials (HEMs), not only because they can serve as tailorable precursors to high-entropy oxides (HEOs) but also because they can have unique high-entropy properties themselves. Many hydroxide crystal structures that are important for various applications are yet to be studied within the context of high-entropy materials, and it is unknown if they can take a high-entropy form (typically five or more incorporated cations). One such material is the dawsonite-type structure, which is a material with applications in both catalysis and ceramics. This work focuses on the adaptation of a dawsonite-type structure (NH4M(OH)2CO3) into a high-entropy material. Through a coprecipitation synthesis method, dawsonite-type materials readily took a high-entropy form with five cations that were equimolar and homogeneously distributed. The specific chemistries investigated were Al, Cr, Fe, and Ga with a fifth cation that was varied with increasing ionic radius (In, Er, Ho, Y, Eu, Ce, La). High-entropy dawsonites also exhibit the ″memory effects″ of non-high-entropy dawsonites. This work extends the field of high-entropy materials to include a structure that can serve as a material platform for the synthesis of high-entropy catalytic materials and ceramic powders.