Thin flakes of yttrium hydroxide agglomerated in a manner resembling houses of cards with aging at 10degreesC. The agglomerate then dissociated into fine yttria particles with calcination at >800degreesC. The particle size of the calcined powder increased appreciably as the calcination temperature increased. The shrinkage curve indicated similar densification behavior among undoped yttria powders calcined at 800degrees-1000degreesC, despite considerable particle growth as the calcination temperature increased. Increasing the calcination temperature to >1000degreesC shifted the shrinkage curve appreciably to the high-temperature region. Sulfate-ion-doped yttria particles had round edges, irrespective of calcination temperature, in contrast to the sharp edges of the undoped yttria particles. A calcination temperature of <1000degreesC resulted in skeleton yttria particles, which exhibited poor sinterability. At a calcination temperature >1000degreesC, the skeleton particles dissociated into monodispersed particles that densified easily. When the calcination temperature was >1000degreesC and the average particle sizes were similar, the undoped and sulfate-ion-doped yttria showed similar densification rates. The transparency of the sintered yttria ceramics was dependent on both the calcination temperature and sulfate-ion doping: that is, sulfate-ion doping and calcining at 1100degreesC were both necessary conditions for the fabrication of a transparent body.