| abstract |
A wavelength converter is provided with a light-transmitting substrate and with a thin film that is formed on a surface of the light-transmitting substrate and that contains a phosphor. A sintered body that constitutes the light-transmitting substrate has an average particle size of 5-40 μm. The light-transmitting substrate contains at least 10-500 ppm by mass of MgO. The principal component of the phosphor is an α-sialon that is indicated by the general formula (Ca α ,Eu β ) (Si,Al) 12 (O,N) 16 (provided that 1.5<α+β<2.2, 0<β<0.2, and O/N≦0.04). |