We propose in this paper, to fix the sintering conditions, such as time, temperature, atmosphere and powder nature to yttria, and to discuss only the influence of the grain shape on the sintering capacity. This study proves that not only the spheres are good candidates for further densification, but also grooved grains, or other massive and regular objects. This study gives tools to predict the sintering capacity of a given powder in relation to its grain shape and these predictions may be extended to other powders.