Elastic Moduli of Transparent Yttria

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Abstract
The elastic moduli of yttria (Y2O3) samples that were made from powders with various particle morphologies were studied by means of ultrasonic measurements. The soundwave velocities in the longitudinal and transverse modes were measured. The elastic moduli were calculated from the sound velocities and density. For the high‐purity, high‐density (>5000 kg/m3) Y2O3 that was prepared in the present study, the average density and elastic moduli (and their standard deviations) were as follows: density (ρ) of 5020 ± 18 kg/m3, Young's modulus (E) of 179.8 ± 4.8 GPa, shear modulus (G) of 69.2 ± 2.0 GPa, bulk modulus (B) of 148.9 ± 3.0 GPa, and Poisson's ratio (ν) of 0.299 ± 0.004. The average longitudinal and transverse soundwave velocities (Vl and Vt, respectively) were 6931 ± 65 and 3712 ± 49 m/s, respectively. The elastic moduli of lanthana‐strengthened yttria (LSY) were ∼6% lower than those of high‐purity Y2O3, and the nu value for LSY was ∼0.304. It has been argued that soundwave velocity is better than density, in regard to predicting the elastic moduli of fully dense and slightly porous materials. A linear equation that describes the change of the elastic moduli with soundwave velocity alone has been suggested. This equation was applicable to a relative elastic moduli range of 0.75–1.02.