On the correlative microscopy analyses of nano-twinned domains in 2 mol% zirconia alloyed yttrium tantalate thermal barrier material

Formation of nano-twinned domains associated with ferro-elastic transformation in 2 mol.% ZrO2 alloyed YTaO4 has been investigated using a correlative microscopy approach. Transmission Kikuchi diffraction reveals the presence of two phases, monoclinic (M) and tetragonal (T) in the material sintered at 1485 °C for 3 hr. The microstructure comprises of alternate nano-twinned domains with an average spacing of 154.07 ± 42.52 nm. Crystallographic symmetry based spontaneous strain analyses support the observation of single domain state. Ab-initio calculations further indicate the propensity of stabilizing both M and T phases at room temperature as a function of ZrO2 alloying, without any change in chemical composition, as is evidenced by atom probe tomography.