Effect of Divalent Cation-Doping on Sinterability of Yttria

Abstract

The dopant effects of divalent cations, Zn²⁺, Ni²⁺, Mn²⁺ and Mg²⁺, on the sinterability of Y₂O₃ were systematically investigated with a doping concentration of 1 mol% at sintering temperatures in a range from 1100 to 1600^oC in air. The sinterability was improved by the doping and the effect was in the order of Zn²⁺ > Ni²⁺ > Mn²⁺ > Mg²⁺. The relative density of 99% was achieved at 1200^oC in Zn²⁺-doped Y₂O₃, while the relative density reached only 98% even at 1600^oC in undoped Y₂O₃. The grain sizes were increased by the doping. The grain sizes of the cation doped Y₂O₃s sintered at 1300^oC were 0.4-1.0um, whereas that of undoped Y₂O₃ was 0.3um. No abnormal grain growth was observed excepting Zn²⁺-doped Y₂O₃ sintered at 1500^oC. The dopant cations segregated along the grain boundaries without amorphous layers or secondary phase particles. The improved sinterability is probably related to the enhanced grain boundary diffusion due to the segregation of the dopant cation.