Doping effect of divalent cations on sintering of polycrystalline yttria

摘要

The sintering behavior of Y_2O_3 doped with 1 mol% of Ca~(2+),Mg~(2+),Mn~(2+), Ni~(2+), Sr~(2+) or Zn~(2+) was investigated by pressureless sintering in air at a sintering temperature in the range 900-1600℃. The sintering temperature required for full densification in Y_2O_3 was reduced by 100-400 ℃ by the cation doping, while undoped Y_2O_3 was densified at 1600℃. The most effective dopant among the examined cations was Zn~(2+). The grain growth kinetics of undoped and cation-doped Y_2O_3 was described by the parabolic law. The grain boundary mobility of Y_2O_3 was accelerated by doping of the divalent cations. High-resolution transmission electron microscopy (HRTEM) observations and nano-probe X-ray energy dispersive spectroscopy (EDS) analyses confirmed that the dopant cations tended to segregate along the grain boundaries without forming amorphous layers. The improved sinterability of Y_2O_3 is probably related to the accelerated grain boundary diffusion owing to the grain boundary segregation of the dopant cations.