The ornamental design for a ceramic essential oildiffuser, as shown and described.
FIG. 1 is a first perspective view of a ceramic essential oil diffuser showing my new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof; and,
FIG. 9 is a perspective view of another state of the ceramic essential oil diffuser thereof.
The broken lines shown in the drawings depict portions of the ceramic essential oil diffuser in which the design is embodied that form no part of the claimed design.