Aluminum-titanate-based ceramic honeycomb structure, its production method, and starting material powder for producing same

1. A ceramic honeycomb structure having a large number of flow paths partitioned by porous cell walls, said cell walls comprising at least main crystals of aluminum titanate, in which MgO and SiO 2 are dissolved to form a solid solution, and glass phases; said glass phases containing 40-80% by mass of SiO 2 and 1-20% by mass of MgO; the average size of said glass phases being 30 μm or less in a cross section of said cell walls; and the area ratio of said glass phases to the total area of said main crystals of aluminum titanate and said glass phases being 2-7.5% in a cross section of said cell walls.

2. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein the amounts of MgO and SiO 2 dissolved in said main crystals are 0.2-5% by mass and 0.1-1.5% by mass, respectively.

3. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein said porous cell walls have porosity of 40-70%, an average pore size of 10-40 μm, and a pore distribution deviation σ[=log(D20)−log(D80)] of 0.4 or less, wherein D20 represents a pore size (μm) at a pore volume corresponding to 20% of the total pore volume, and D80 represents a pore size (μm) at a pore volume corresponding to 80% of the total pore volume, both in a curve representing the relation between the pore size and the cumulative pore volume (pore volume accumulated in a range from the maximum pore size to a particular pore size), and D80<D20.

4. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein said cell walls have air permeability of 2×10 −12 m 2 or more.

5. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein said honeycomb structure has an A-axis compression strength of 4 MPa or more.

6. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein said cell walls have a thermal expansion coefficient of 12×10 −7 /° C. or less.

7. The aluminum-titanate-based ceramic honeycomb structure according to claim 1 , wherein 95% or more of the aluminum titanate remains after said cell walls are kept in an atmosphere at 1100° C. for 100 hours.

8. A ceramic honeycomb structure having a large number of flow paths partitioned by porous cell walls, said cell walls comprising at least main crystals of aluminum titanate, in which MgO and SiO 2 are dissolved to form a solid solution, and glass phases; said glass phases containing 40-80% by mass of SiO 2 and 1-20% by mass of MgO; the average size of said glass phases being 30 μm or less in a cross section of said cell walls; and the mass ratio of said glass phases to the total of said main crystals of aluminum titanate and said glass phases being 1.6-4.9% by mass.

9. A starting material powder for producing an aluminum-titanate-based ceramic honeycomb structure comprising at least main crystals of aluminum titanate, in which MgO and SiO 2 are dissolved to form a solid solution, and glass phases, said starting material powder comprising 100 parts by mass of a powder material comprising alumina powder containing 0.05-0.5% by mass of Na 2 O and titania powder containing 0.01-0.5% by mass of Na 2 O at a molar ratio of 47/53 to 53/47, and at least 1-6 parts by mass of silica powder, and 0.5-5 parts by mass of magnesia source powder having an average particle size of 5 μm or less.

10. The starting material powder for producing an aluminum-titanate-based ceramic honeycomb structure according to claim 9 , wherein said alumina powder contains 0.21-0.5% by mass of Na 2 O.