What types of ceramics are formed by heat?

Ceramic is a porous material. It has many small air pockets in it which help to reduce heat conduction. The heat does not transfer easily to air so the transfer is held back by these pockets and the heat is retained in the contained liquid or material. The atomic structure of ceramic accounts for its ability to retain heat due to the configuration of bound atoms or ions. A more crystalline structure will have less heat transferred and will retain more heat.