Dynamic study of ammonium dawsonite doped with yttrium transformation at elevated temperatures

Abstract

Co-precipitation of alumina/YAG precursor from aluminum and yttrium nitrates solution with ammonium carbonate results in dawsonite (NH 4 Al(OH) 2 CO 3 ). Its crystallographic parameters differ from the compound precipitated without the yttrium additive. It indicates that yttrium ions become incorporated into the dawsonite structure. The DSC/TG and X-ray measurements show decomposition of dawsonite at elevated temperature resulting in c-Al 2 O 3 which transforms to d and h modifications at still higher temperatures. The full transformation to a-Al 2 O 3 and YAG occurs at temperatures higher than 1,230°C.

Synthesis and Characterization of High-Entropy Dawsonite-Type Structures

“…The multicationic dawsonite-type structures appear to have an increase in crystallite size compared to the single-cation Al-Daw sample. Similar increases in crystallite size have been observed in studies with two cations (yttrium and aluminum), 43 and this trend was attributed to yttrium ions slowing down the dawsonite crystallite growth. For two of the largest cations in this study, lanthanum and europium, reflections from additional phases were observed, specifically carbonate crystalline phases at 2θ = 10.3 and 18.3°.…”