Comparison of Solid‐State and Spray‐Pyrolysis Synthesis of Yttrium Aluminate Powders

Abstract

The influence of precursor characteristics and synthesis conditions on the formation of yttrium aluminum garnet, Y 3 Al 5 O 12 (YAG), was investigated using “single‐source” precursors (cohydrolyzed yttrium and aluminum alkoxides and yttrium aluminum glycolates) and “multiple‐source” precursors (mixtures of metal nitrates and mixtures of separately hydrolyzed yttrium and aluminum alkoxides). Phase‐pure YAG was formed only in the solid‐state thermal decomposition experiments. The lack of formation of YAG in all the spray‐pyrolysis experiments was ascribed to the short heating times and fast heating rates, which resulted in the formation of kinetic products. In the case of the metal nitrates, an additional factor that influenced product formation was the difference in thermal reactivity of the precursors. It was concluded that the formation of complex metal oxide materials by conventional or aerosol routes is not necessarily achieved by the use of a chemically homogeneous precursor, such as a single‐source precursor. It also was necessary to ensure that the precursors and intermediates have similar thermal decomposition temperatures to avoid phase segregation in the initial stages of thermal decomposition.