Black pottery is baked through the infiltration of carbon and thus through the formation of carbon fibres during the baking process. For this reason, I would call it "carbon infiltrated black pottery" or simply "black pottery."

http://www.deesenclassic.com/p2.html

"The history of black pottery can be traced back thousands of years. Using an advanced technique to seal the kilns, this technique allowed infiltrating carbon to bake the pottery black. The technique of the black pottery arts has resurfaced in China, producing some of the most exquisite pieces available for today's contemporary home design. This combination of primitive technique and modern design creates a product of unique beauty."

FYI