Abstract: A cordierite-based ceramic(s) is provided where a main crystalline phase thereof is a cordierite crystalline phase, a content of Mg is 13.2% by mass or more and 13.8% by mass or less in an MgO equivalent, a content of Al is 26.0% by mass or more and 32.1% by mass or less in an Al2O3 equivalent, a content of Bi is 1.6% by mass or more and 4.6% by mass or less in a Bi2O3 equivalent, a content of B is 1.5% by mass or more and 6.8% by mass or less in a B2O3 equivalent, and a content of Si is 49.4% by mass or more and 51.4% by mass or less in an SiO2 equivalent.

Abstract: A silicon nitride cutting tool comprising a sintered product is disclosed. The sintered product comprises silicon nitride, at least one rare earth element compound, and a magnesium compound. The silicon nitride cutting tool further comprises a surface region and an inside region comprising the sintered product with varying content ratios of component compounds to provide enhanced wear and fracture resistance.

Abstract: A sintered product of silicon nitride includes a crystal phase mainly having silicon nitride crystal grains and an amorphous grain-boundary phase located on the grain boundaries of the silicon nitride crystal grains. The grain-boundary phase contains lanthanum, aluminum, magnesium, silicon, and oxygen. The sintered product described above contains 0.1% by mass or more of lanthanum on an oxide basis, 0.05 to 0.6% by mass of aluminum on an oxide basis, 0.3% by mass or more of magnesium on an oxide basis, and 2.5% by mass or less of oxygen. The total amount of lanthanum on an oxide basis, aluminum on an oxide basis, and magnesium on an oxide basis is 3.5% by mass or less.

Abstract: A silicon nitride cutting tool comprising a sintered product is disclosed. The sintered product comprises silicon nitride, at least one rare earth element compound, and a magnesium compound. The silicon nitride cutting tool further comprises a surface region and an inside region comprising the sintered product with varying content ratios of component compounds to provide enhanced wear and fracture resistance.

Abstract: A sintered product of silicon nitride includes a crystal phase mainly having silicon nitride crystal grains and an amorphous grain-boundary phase located on the grain boundaries of the silicon nitride crystal grains. The grain-boundary phase contains lanthanum, aluminum, magnesium, silicon, and oxygen. The sintered product described above contains 0.1% by mass or more of lanthanum on an oxide basis, 0.05 to 0.6% by mass of aluminum on an oxide basis, 0.3% by mass or more of magnesium on an oxide basis, and 2.5% by mass or less of oxygen. The total amount of lanthanum on an oxide basis, aluminum on an oxide basis, and magnesium on an oxide basis is 3.5% by mass or less.