Synthesis and characterization of Y₂Ti₂O₇ nanoparticles from Y–Ti hydride nanocomposite at a low sintering temperature

The Y–Ti hydrides nanoparticles were prepared by hydrogen plasma-metal reaction (HPMR) method. Transmission electron microscopy (TEM) observation revealed that they were spherical in shape and ranged from 5 to 75 nm with a mean diameter of 31 nm. Each nanoparticle contained different hydride phases (YH₂, YH₃ and TiH_1.924), and there existed dislocations to relax lattice misfit strain and minimize the interfacial energy. The hydride nanocomposite started to oxidize at 218 °C during annealing in air, and the pyrochlore-type Y₂Ti₂O₇ nanoparticles of single crystalline were fabricated successfully at a low sintering temperature of 900 °C for 1 h. The Y₂Ti₂O₇ nanoparticles of axiolitic shape had an average size of 70 nm, much smaller than the conventional Y₂Ti₂O₇ prepared by sintering Y and Ti oxides above 1300 °C. The formation of Y₂Ti₂O₇ nanoparticles from the hydride nanocomposite at a low temperature and short reaction time can be attributed to the very short diffusion distance of Y and Ti at nanoscale, and the accelerated diffusion rate due to the strained interface of different hydride phases. The novel strategy opens a new way to prepare the nanosized pyrochlore-type oxides at a low temperature.