Effect of Solid State Synthesis Parameters on Indium-Tin-Copper-Zinc Medium Entropy Oxides

InaSnbZncOx based ceramics (ITZO) CCOs hold significant potential in semiconducting, optoelectronic, and energy harvesting/conversion/storage applications due to their highly tunable compositions and crystal structures. Here, we aim to expand the compositional landscape of this system towards equimolar stoichiometries and configurational entropy stabilized single-phase crystal structures. This may offer novel property control through unique element combinations, lattice disorder, bonding environments and electronic structures. Here, we use simple solid-state sintering to systematically investigate the roles of stoichiometry, sintering temperature, sintering time and cooling rate on the final phase fraction of the equimolar medium entropy compositions InZnSnOx and InZnSnCuOx, which are designed to reduce the overall In content while introducing Cu-derived functionality. These studies reveal fundamental relationships between ceramic processing parameters and final phase fractions, highlighting key trends in the amount of dominant phases including In2O3-based cubic c-(InxZnySnzCuw)2O3 and near-equimolar entropy stabilized hexagonal h-In0.8Zn0.6Sn0.6O3. Despite the large mismatch in constituent binary oxide crystal structures and cation radii and valence, we are able to tailor the fraction of primary/dominant phases from relatively dilute to near-equimolar concentrated solid solutions.