Phase evolution and thermal behaviors of the solid-state reaction between SrCO3 and Al2O3 to form SrAl2O4 under air and CO2-air atmospheres

The solid-state reactions between SrCO3 and Al2O3 forming SrAl2O4 under air and CO2-air atmospheres were investigated. The solid-state reaction between SrCO3 and Al2O3 under a CO2 atmosphere can be separated into multiple reaction stages. The first stage is attributed to the formation of SrAl2O4 resulting from the reaction between SrCO3 and Al2O3. The diffusion of Al2O3 through the product layer then takes place to continue the reaction. At a higher temperature, the Sr3Al2O6 formation reaction occurs due to the chemical reaction between SrCO3 and SrAl2O4. The SrCO3 is thermally finally decomposed. The resulting SrO may diffuse rapidly through the product layer, producing pure SrAl2O4 formation via a complicated diffusion process at a much higher temperature. These reaction stages occur at very close temperatures under an air atmosphere, leading to a complex reaction between the solids in air.