A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls provided, surrounding a plurality of cells which serve as fluid through channels extending from an inflow end face to an outflow end face, and porous plugging portions provided either at the ends on the inflow end face or the outflow end face of the cells, wherein the plugging portions are composed of a porous material, the honeycomb structure has a central region and a circumferential region, and a ratio of an area of the circumferential region with respect to that of the central region ranges from 0.1 to 0.5, a plugging length L1 in the cell extending direction of a central plugging portion in the central region is larger than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 7 to 9 mm, and L2 from 3 to 6 mm.

A method for producing a honeycomb structure includes: a forming step of extruding a forming raw material containing a ceramic raw material to obtain a honeycomb formed body, the honeycomb formed body including: an outer peripheral wall; and partition walls disposed on an inner side of the outer peripheral wall, the partition walls defining a plurality of cells, each of the plurality of cells extending from one end face to the other end face to form a flow passage; a drying step of drying the honeycomb formed body to obtain a honeycomb dried body; and a firing step of firing the honeycomb dried body to obtain a honeycomb fired body. The forming step includes extruding the forming raw material to produce a honeycomb formed body in which a part of the partition walls is lost so that some of the cells are connected to each other.

A method for producing a honeycomb structure includes: a forming step of extruding a forming raw material containing a ceramic raw material to obtain a honeycomb formed body, the honeycomb formed body including: an outer peripheral wall; and partition walls disposed on an inner side of the outer peripheral wall, the partition walls defining a plurality of cells, each of the plurality of cells extending from one end face to the other end face to form a flow passage; a drying step of drying the honeycomb formed body to obtain a honeycomb dried body; and a firing step of firing the honeycomb dried body to obtain a honeycomb fired body. The forming step includes extruding the forming raw material to produce a honeycomb formed body in which a part of the partition walls is lost so that some of the cells are connected to each other.

A porous honeycomb structure including cell channels passing through an interior of the porous honeycomb structure and partitioned by porous partition walls, wherein the porous partition walls include skeleton portions containing an aggregate and a bonding material, and pore portions formed among the skeleton portions and through which a fluid can flow; and the porous partition walls have a porosity of 40 to 48% as measured by a mercury intrusion method, and a cumulative 50% pore diameter (D50) from a large pore side of 6 to 10 μm in a volume-based cumulative distribution of pore diameters measured by the mercury intrusion method, and a maximum pore diameter observed with a scanning electron microscope of 40 μm or less, and a ratio of a contact area between the aggregate and the bonding material to a surface area of the bonding material observed with the scanning electron microscope of 61 to 80%.

A porous honeycomb structure including cell channels passing through an interior of the porous honeycomb structure and partitioned by porous partition walls, wherein the porous partition walls include skeleton portions containing an aggregate and a bonding material, and pore portions formed among the skeleton portions and through which a fluid can flow; and the porous partition walls have a porosity of 40 to 48% as measured by a mercury intrusion method, and a cumulative 50% pore diameter (D50) from a large pore side of 6 to 10 μm in a volume-based cumulative distribution of pore diameters measured by the mercury intrusion method, and a maximum pore diameter observed with a scanning electron microscope of 40 μm or less, and a ratio of a contact area between the aggregate and the bonding material to a surface area of the bonding material observed with the scanning electron microscope of 61 to 80%.

A method for producing a conductive honeycomb structure includes: a forming step of extruding a forming raw material to obtain a honeycomb formed body; a drying step of drying the honeycomb formed body to obtain a honeycomb dried body; and a firing step of firing the honeycomb dried body to obtain a honeycomb fired body. The forming step includes controlling a volume fraction of a portion that can form pores of the honeycomb formed body so that an absolute value of a difference in the volume fraction of the portion that can form the pores in predetermined regions of the honeycomb formed body relative to a previously set, predetermined porosity of the honeycomb fired body is within 0.5%. The predetermined porosity is a porosity preset for each of the predetermined regions of the honeycomb fired body.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion provided at an open end on a first end face side or a second end face side of the cells, wherein the partition wall is composed of a material containing cordierite as a main component, a porosity of the partition wall is 60 to 70%, an average pore diameter of the partition wall is 20 to 30 μm, an open porosity of pores existing at the partition wall surface and having equivalent circle diameters exceeding 1.5 μm is 31% or more, and, in a pore diameter distribution which indicates a cumulative pore volume of the partition wall, a half-value width of a first peak including a maximum value of a log differential pore volume is 0.20 or less.

A honeycomb structure includes: an outer peripheral wall; and partition walls disposed on an inner side of the outer peripheral wall, the partition walls defining a plurality of cells, each of the plurality of cells extending from one end face to the other end face to form a flow path for a fluid. The partition walls and the outer peripheral wall include ceramics containing at least silicon. A content of silicon in the ceramics is 30% by mass or more. A concentration of at least one dopant in the silicon is from 10.sup.16 to 5×10.sup.20/cm.sup.3.

A honeycomb structure includes: an outer peripheral wall; and partition walls disposed on an inner side of the outer peripheral wall, the partition walls defining a plurality of cells, each of the plurality of cells extending from one end face to the other end face to form a flow path for a fluid. The partition walls and the outer peripheral wall include ceramics containing at least silicon. A content of silicon in the ceramics is 30% by mass or more. A concentration of at least one dopant in the silicon is from 10.sup.16 to 5×10.sup.20/cm.sup.3.

Honeycomb bodies, honeycomb structures and extrusion dies, including a transition structural component. A honeycomb structure (100) includes a plurality of interconnected webs (106) defining a plurality of cell channels (108) in a honeycomb matrix (109) having a central axis (110) orthogonal to its transverse cross-section. Radial webs (116) diverge outwardly from the central axis (110). Radial webs (116) include a first radial web (150) and a second radial web (152). Tangential webs (120) are arranged concentrically with respect to the central axis (110), wherein at least one of the tangential webs (120) is a tangential transition web (142). At least one transition structural component (140) is located radially inward from the tangential transition web (124) and includes a first inclined web (144) having a first end (144A) coupled to the first radial web (150) and a second inclined web (146) having a first end (146A) coupled to the second radial web (152). Extrusion dies configured to make the honeycomb structures are provided, as are other aspects.