Obviously, the relative density of the HA component increased significantly with the increase in the initial DCPD content (Fig. 2(a)) and then stabilized at ~85%, which is slightly inferior to the relative density of co-precipitated HA after cold sintering (over 90%) [5,6]. Therefore, we believe that the addition of DCPD should have a significant promotion effect on the densification of the cold-sintered HA. However, this effect reached its limit when the initial DCPD content reached 30 wt%, which might be related to local agglomeration of the HA particles, as will be described below.