Light wavelength conversion member and light emission device

An optical wavelength conversion member comprising a polycrystalline ceramic sintered body containing, as main components, Al2O3 crystal grains and crystal grains of a component represented by formula A3B5O12:Ce, the optical wavelength conversion member being characterized in that:

• each of A and B of the A3B5O12 is at least one element selected from the following element groups:
• A:
• Sc, Y, and lanthanoids (except for Ce), and
• B:
• Al and Ga;
• and
• the following relations are satisfied:
• 0%≤X≤25%,
• 9%≤Y≤45%, and
• 48%≤Z≤90%,
• wherein X represents a proportion corresponding to the ratio a/N, Y represents a proportion corresponding to the ratio b/N, and Z represents a proportion corresponding to the ratio c/N, wherein N represents the total number of A3B5O12:Ce crystal grains present in a 20 μm square region of a cross section of the ceramic sintered body;
• a represents the number of A3B5O12:Ce crystal grains present in Al2O3 crystal grains;
• b represents the number of A3B5O12:Ce crystal grains each being present at an Al2O3 crystal grain boundary and not in contact with another A3B5O12:Ce crystal grain;
• and c represents the number of A3B5O12:Ce crystal grains each being present at an Al2O3 crystal grain boundary and in contact with one or more other A3B5O12:Ce crystal grains,
• wherein the ceramic sintered body contains A3B5O12:Ce crystal grains in an amount of 5 to 50 vol. %, and
• wherein the amount of Ce is 10.0 mol % or less (exclusive of 0) relative to A in the A3B5O12.

An optical wavelength conversion member comprising a polycrystalline ceramic sintered body containing, as main components, Al2O3 crystal grains and crystal grains of a component represented by formula A3B5O12:Ce, the optical wavelength conversion member being characterized in that:

• each of A and B of the A3B5O12 is at least one element selected from the following element groups:
• A:
• Sc, Y, and lanthanoids (except for Ce), and
• B:
• Al and Ga;
• and
• the following relations are satisfied:
• 0%≤X≤25%,
• 9%≤Y≤45%, and
• 48%≤Z≤90%,
• wherein X represents a proportion corresponding to the ratio a/N, Y represents a proportion corresponding to the ratio b/N, and Z represents a proportion corresponding to the ratio c/N, wherein N represents the total number of A3B5O12:Ce crystal grains present in a 20 μm square region of a cross section of the ceramic sintered body;
• a represents the number of A3B5O12:Ce crystal grains present in Al2O3 crystal grains;
• b represents the number of A3B5O12:Ce crystal grains each being present at an Al2O3 crystal grain boundary and not in contact with another A3B5O12:Ce crystal grain;
• and c represents the number of A3B5O12:Ce crystal grains each being present at an Al2O3 crystal grain boundary and in contact with one or more other A3B5O12:Ce crystal grains,
• wherein the ceramic sintered body contains A3B5O12:Ce crystal grains in an amount of 5 to 50 vol. %,
• wherein the amount of Ce is 10.0 mol % or less (exclusive of 0) relative to A in the A3B5O12, and
• wherein Al2O3 crystal grains have a mean grain size of 0.3 to 10 μm, and A3B5O12:Ce crystal grains have a mean grain size of 0.3 to 5 μm.