In this section, the sintering cond

In this section, the sintering conditions were set to 1700 ◦C for 3 h under vacuum and the values of relative densities and grain size are compared for all yttria pellets. The only differences between the samples are the initial grain morphology of the yttria powder as shown in Fig. 1. The relative grain densities of the isostatically pressed pellets are presented in Table 1, as well as the relative densities and the grain sizes. What is striking is that the values of relative density and grain size (Table 1) depend strongly on the initial grain shape and size, and we propose the following model to explain the differences observed.