Honeycomb ceramic substrates, honeycomb extrusion dies, and methods of making honeycomb ceramic substrates

A honeycomb ceramic substrate, comprising:

• a lattice of intersecting walls defining a honeycomb network of flow channels extending between an inlet end and an outlet end of the honeycomb substrate, wherein a first flow channel is defined by a plurality of channel walls of the intersecting walls with at least two of the plurality of channel walls including concave inner surfaces facing a center of the first flow channel, the concave inner surfaces extending from central portions of each of the concave inner surfaces to concave corner portions facing the center of the first flow channel, the concave corner portions located on either end of each concave inner surface, the concave corner portions being where each of the plurality of channel walls intersects with another one of the plurality of channel walls wherein the concave inner surfaces of the channel walls are continuously curved towards the center throughout a length of the channel walls between corresponding ones of the corner portions, a second flow channel adjacent to the first flow channel and sharing a common channel wall, wherein one side of the common channel wall comprises a concave inner surface of the concave inner surfaces and an opposing side the common channel wall includes an opposing concave inner surface facing a center of the second flow channel.