Microstructural Evolution of Dy 2 O 3 -TiO 2 Powder Mixtures during Ball Milling and Post-Milled Annealing

摘要

The microstructural evolution of Dy 2 O 3 -TiO 2 powder mixtures during ball milling and post-milled annealing was investigated using XRD, SEM, TEM, and DSC. At high ball-milling rotation speeds, the mixtures were fined, homogenized, nanocrystallized, and later completely amorphized, and the transformation of Dy 2 O 3 from the cubic to the monoclinic crystal structure was observed. The amorphous transformation resulted from monoclinic Dy 2 O 3 , not from cubic Dy 2 O 3 . However, at low ball-milling rotation speeds, the mixtures were only fined and homogenized. An intermediate phase with a similar crystal structure to that of cubic Dy 2 TiO 5 was detected in the amorphous mixtures annealed from 800 to 1000 °C, which was a metastable phase that transformed to orthorhombic Dy 2 TiO 5 when the annealing temperature was above 1050 °C. However, at the same annealing temperatures, pyrochlore Dy 2 Ti 2 O 7 initially formed and subsequently reacted with the remaining Dy 2 O 3 to form orthorhombic Dy 2 TiO 5 in the homogenous mixtures. The evolutionary mechanism of powder mixtures during ball milling and subsequent annealing was analyzed.