The honeycomb filter includes a honeycomb substrate having porous partition walls defining a plurality of cells and plugging portions. In a cross section, the cells are arranged so that a periphery of an inlet plugged cell including an open end whose shape is a square in which a length of one side is L1 is surrounded with four rectangular outlet plugged cells each including an open end whose shape is a rectangle in which a length of one side is L1 and a length of the other side is L2 (L1>L2) and four square outlet plugged cells each including an open end whose shape is a square in which a length of one side is L2. A partition wall center distance a, a partition wall center distance b and a partition wall thickness t satisfy the following equation (1):
0.95<b/at<1.90   (1).

The present disclosure relates to porous ceramic compositions and porous ceramic articles, such as honeycomb structure bodies and porous ceramic filters. In various embodiments, a particulate filter is disclosed herein; in some of these embodiments, the particulate filter is a gasoline particulate filter (GPF) and is suitable for use with a gasoline engine and treating its exhaust, and in some of the embodiments, the particulate filter is a diesel particulate filter (DPF) and is suitable for use with a diesel engine and treating its exhaust.

A ceramic honeycomb structure comprising large numbers of flow paths longitudinally formed by cell walls arranged in a lattice pattern in cross section, and an outer peripheral wall formed around the flow paths; in a cross section perpendicular to the longitudinal direction, fan-shaped bulges projecting in a fan shape toward the flow paths from cell wall intersections at which the cell walls are crossing; the circumscribed circles of circular portions of the fan-shaped bulges at all cell wall intersections having a constant radius; and when the distance between the center point of the circumscribed circle and the center point of the cell wall intersection is defined as a center point distance S, a center point distance So in the outer peripheral portion of the ceramic honeycomb structure and a center point distance Sc in the center portion meeting Sc<So.

In a porous body, a surface layer thickness Ts takes a relatively small value satisfying P≧0.54 Ts (formula (1)), the surface layer thickness Ts being derived by a microstructure analysis using the porous-body data that is prepared through three-dimensional scanning of a region including a surface (inflow plane 61) of the porous body. Here, P denotes a porosity [%] of the porous body, and 0%<P<100% and 0 μm<Ts are assumed. The surface layer thickness Ts is derived as a distance in a thickness direction (X direction) between a surface-layer region start plane 92 in which a straight-pore opening ratio becomes 98% or less for the first time and a surface-layer region end plane 93 in which the straight-pore opening ratio becomes 1% or less for the first time.

A plugged honeycomb structure in which in a cross section of a honeycomb structure body which is perpendicular to an extending direction of cells, inflow cells are disposed to surround an outflow cell, and the number of the inflow cells is larger than the number of the outflow cells, and the cross section has a plurality of intersecting portions of partition walls each defining the inflow cells which are adjacent to each other, and in 60% or more of a total number of the intersecting portions, a relation between a diameter (D.sub.1) of a circle inscribed in the intersecting portion and a diameter (D.sub.0) of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies D.sub.1/(√2×D.sub.0)=1.20 to 1.80

A porous ceramic honeycomb body (10) including intersecting walls that form channels (22) extending axially from a first end face to a second end face and layered plugs (62) comprised of a first layer (64) disposed on channel walls and a second layer (66) disposed inward toward an axial center of each respective channel on the first layer. The plugs seal at least one of a first portion of the channels at the first end face and a second portion of channels at the second end face of the porous ceramic honeycomb body.

A honeycomb structure includes a honeycomb structure body that includes a porous partition wall which defines a plurality of cells serving as through channels of fluid and extending from an inflow end face as one end face to an outflow end face as the other end face, and a circumferential wall arranged on a circumferential surface of the honeycomb structure body. The circumferential wall has a thickness of 0.5 to 4.0 mm, a gap path is formed along a surface of the circumferential wall inside the circumferential wall, the gap path has a width of 0.4 to 4.0 mm, and has a height of 50 to 99% of the thickness of the circumferential wall, and a total length of the gap path is 1000% or more of a length in the cell extending direction of the honeycomb structure body.

The honeycomb structure includes a honeycomb structure body having porous partition walls, and a plugging portion disposed in one of open ends of each cell, a thickness of the partition walls is 0.30 mm or more and 0.51 mm or less, a cell density is 30 cells/cm.sup.2 or more and 93 cells/cm.sup.2 or less, a filtration area (cm.sup.2) of inflow cells included per cm.sup.3 of the honeycomb structure body is defined as an inflow side filtration area G (cm.sup.2/cm.sup.3), a value obtained by dividing a pore volume Vp (cm.sup.3) formed in the partition walls by a total volume Va (L) including the cells is defined as a pore volume ratio A (cm.sup.3/L), and in this case, a product of the inflow side filtration area G (cm.sup.2/cm.sup.3) and the pore volume ratio A (cm.sup.3/L) is 1800 cm.sup.2/L or more and 3200 cm.sup.2/L or less.

A honeycomb structure comprising: a honeycomb structure body that includes a plurality of porous partition walls and intersection parts, and a catalyst layer, wherein the porosity of the partition wall is 20 to 70%, the average pore diameter of the pores in the partition wall is 1 to 60 μm, a plurality of the partition walls includes a notched partition wall having a recessed part in which at least one end is notched, the ratio of the notched partition wall in the partition walls is 1 to 100%, the recessed part of the notched partition wall has a depth of 10 to 200% of the standard length, and the recessed part of the notched partition wall is a part having a width of 33 to 100% of the standard width.

A honeycomb filter includes a honeycomb structure body having porous partition walls defining a plurality of cells which become through channels for fluid, plugging portions disposed in open ends of the cells, and a protective layer disposed to cover at least the surface of the honeycomb structure body, each of the honeycomb structure body and the plugging portion has a structure constituted of aggregates made of silicon carbide and a bonding material which bonds the aggregates to one another, the protective layer is a layer in which silicon is present as much as 40 mass % or more and oxygen is present as much as 40 mass % or more and a thickness is 0.5 μm or more, and an outer end face of both end faces of the plugging portion has an exposed region in which the protective layer is not disposed.