Optical wavelength conversion member and light-emitting device
An optical wavelength conversion member and a light-emitting device including the optical wavelength conversion member. The optical wavelength conversion member ( 9 ) is formed of a ceramic sintered body having a fluorescent phase containing fluorescent crystal grains as a main component and a translucent phase containing translucent crystal grains as a main component. Crystal grains of the fluorescent phase have a composition represented by formula A 3 B 5 O 12 :Ce, where the element A is selected from Sc, Y, and lanthanoids (except for Ce), and the element B is selected from Al and Ga. In the optical wavelength conversion member ( 9 ), 0.3<a<34 and 300 μm<y<1,050 μm are satisfied, wherein a represents the area ratio of the translucent phase to the fluorescent phase in a cross section of the optical wavelength conversion member ( 9 ), and y represents the interfacial length of the fluorescent phase.
1. An optical wavelength conversion member comprising a ceramic sintered body having a fluorescent phase containing fluorescent crystal grains as a main component and a translucent phase containing translucent crystal grains as a main component, wherein
the crystal grains of the fluorescent phase have a composition represented by formula A 3 B 5 O 12 :Ce, and each of the element A and the element B 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:
0.3<a<34 and 300 μm<y<1,050 μm,
wherein a represents the ratio of the area of the translucent phase to the area of the fluorescent phase in a cross section of the optical wavelength conversion member, and y represents the interfacial length of the fluorescent phase.
2. An optical wavelength conversion member according to claim 1 , wherein the following relation is satisfied: 1.1<x<2.1, wherein x represents the ratio of the mean grain size r1 of crystal grains of the translucent phase to the mean grain size r2 of crystal grains of the fluorescent phase; the crystal grains of the translucent phase have a mean grain size r1 of 0.2 μm to 6 μm; and the crystal grains of the fluorescent phase have a mean grain size r2 of 0.1 μm to 4 μm.
3. An optical wavelength conversion member according to claim 1 , wherein the crystal grains of the translucent phase have a composition of Al 2 O 3 .
4. An optical wavelength conversion member according to claim 1 , wherein the ceramic sintered body contains a compound represented by formula A 3 B 5 O 12 :Ce in an amount of 3 vol. % to 70 vol. %.
5. An optical wavelength conversion member according to claim 1 , wherein the Ce content of the compound represented by formula A 3 B 5 O 12 :Ce is 0.1 mol % to 1.0 mol % relative to the element A of the compound.
6. A light-emitting device comprising an optical wavelength conversion member as recited in claim 1 .