Patent ID: 8513876

Claim:
A fluorescent substance comprising an α-sialon crystal structure having the same crystal structure with an α-type silicon nitride crystal, which has a peak emission wavelength within the range of 560 to 610 nm and includes a composition represented by the following composition formula: M(0) x M(1) y M(2) z Si 12-(m+n) Al (m+n) O n N 16-n where M(0) represents one or two elements selected from Sr and La; M(1) represents one or more elements selected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb; M(2) represents one or more elements selected from Li, Na, Be, Mg, Ca, Ba, Sc, Y, Gd, and Lu; x, y, and z represent the composition ratio satisfy the inequations of 0.01≦x≦4, 0.001<y≦2, 0≦z≦2, and 0≦z/x≦⅔; and m and n represent the composition ratio satisfy the inequations of 0.8·me≦m≦1.2·me and 0≦n≦4 provided that me=x·v(0)+y·v(1)+z·v(2) (where v(0) represents a valence of the M(0) ion, v(1) represents a valence of the M(1) ion, and v(2) represents a valence of the M(2) ion).