The hexacelsian-to-celsian phase transformation in Ba 1– x Sr x Al 2 Si 2 O 8 is of interest for environmental barrier coating applications. Plasma-sprayed microstructures were heat treated above 1100°C and the kinetics of the hexacelsian-to-celsian transformation were quantified. Activation energies for bulk and crushed materials were determined to be ∼340 and ∼500kJmol −1 , respectively. X-ray diffraction and electron backscattered diffraction were used to establish how plasma spraying barium- and strontium-doped aluminosilicate effectively reduces the energy required for its transformation.