Patent ID: 8449645

Claim:
A ceramic honeycomb structure having a large number of flow paths defined by porous cell walls, said porous cell walls being composed of cordierite crystals, mullite crystals, corundum crystals and/or spinel crystals; the percentage of the X-ray diffraction intensity of the cordierite crystals being 72% or more and less than 85%, the percentage of the X-ray diffraction intensity of the mullite crystals being 15-25%, and the percentage of the total X-ray diffraction intensity of the corundum crystals and the spinel crystals being 5% or less, per the total X-ray diffraction intensity of these crystals, wherein the X-ray diffraction intensity of each crystal is the intensity of a main peak converted from each X-ray diffraction intensity of a (102) plane of cordierite, a (110) plane of mullite, a (104) plane of corundum and a (220) plane of spinel; said porous cell walls having a true density of 2.55-2.70 g/cm 3 , a mean pore diameter of 10-20 μm, and a porosity of 50-65%; the volume of pores having diameters exceeding 50 μm being 8-25% of the total pore volume; the volume of pores having diameters of less than 10 μm being 16-25% of the total pore volume; and the pore diameter distribution deviation σ[=log(D 20 )−log(D 80 )] being 0.5 or less, wherein D 20 represents a pore diameter (μm) at a pore volume corresponding to 20% of the total pore volume, and D 80 similarly represents a pore diameter (μm) at a pore volume corresponding to 80% of the total pore volume, on a curve showing the relation between a pore diameter and a cumulative pore volume obtained by accumulating a pore volume from the maximum pore diameter to a particular pore diameter, and D 80 <D 20 .