Polymeric Steric Entrapment Synthesis of Compositionally Complex Rare‐Earth Aluminum Garnets (CCREAGs)

This work focuses on the polymeric steric entrapment (PSE) technique to synthesize a series of ( n RE 1/ n ) 3 Al 5 O 12 , or compositionally complex rare‐earth aluminum garnet (CCREAG) compositions, where RE represents a variety of rare‐earth cations and n is the number of cations occupying the shared position. Using PSE, CCREAGs crystallized at ∼900°C. Compositions spanned n from 1 to 10, featuring RE ionic radii averages (IR ave ) ranging from 0.977 to 1.160 Å, and accompanying size disorder, δ (%), ranging from 0.00 to 6.70. Single‐phase garnets were formed over the entire range of compositional complexity (i.e., n = 1 up to n = 10) and size disorder; however, once IR ave was approximately greater than 1.027 Å, multiphase assemblages resulted. The larger RE cations that do not form the garnet structure on their own, can be incorporated into the garnet structure by combining with smaller RE cations to decrease the IR ave . The lattice parameters of the CCREAGs increased from 11.995(1) to 12.081(2) Å, with increased IR ave . The PSE technique resulted in a homogeneous distribution of RE species within asymmetric and porous particles. This study provides guidance for exploring and designing new CCREAGs using a facile technique.