Effect of the sulfate ion exerted on densification of yttria

Abstract

Ammonia aqueous solution was added to yttrium nitrate aqueous solution kept at 10 °C, yttrium hydroxide was precipitated and sulfate ion was added. This precursor was calcined at 1100 °C, pressed isostatically under 100 MPa pressure and the powder compact was vacuum-sintered at 1700 °C for 2h. Precursors were characterized by XRD, SEM, TG-DTA, and chemical analysis. Calcined powders were analyzed by SEM, BET surface area, and particle size distribution measurement. When the amount of addition of sulface ion (SO₄^2-/Y³⁺) WAS 1-20%, the sintered compact was transparent. However, the sintering compact was opaque when the amount of addition exceeded 20%.