This work aimed at proposing new ways to predict the densification capacity of a powder, only depending on its grain shape, and by using a thermodynamic model. This model allows us to choose the initial powder morphology in relation with the desired functionality of the ceramic such as density. Generally speaking, even if spheres remain a good candidate for highly efficient sintering, other morphologies, such as grooved particles, or very regular particles also display very good densification capacity. Tools have also been proposed to think through, step by step, the influence of the morphology on the sintering time and densification capacity. Results proposed for yttria powders may be applicable to other powders nature provided that no other sintering phenomena occur.