Patent ID: 8043528

Claim:
An yttrium silicon oxynitride luminescent material comprising: a crystalline phase including Y, Si, O and N; and an activator comprising Tb and Ce, a molar fraction x1 of the Tb based on a total number of moles of Y, Tb and Ce being confined to a range defined by expression 1, below, and a molar fraction y1 of the Ce based on the total number of moles of Y, Tb and Ce being confined to a range defined by expression 2 below; 0 <x 1≦0.6 expression 1; 0 <y 1≦0.2 expression 2, wherein the luminescent material has a composition represented by formula A1, below: (Y 1−x1−y1 ,Tb x1 ,Ce y1 ) a Si b O c Nd A1 wherein “a,” “b,” “c” and “d” are confined to the following ranges: 1.9 ≦a≦ 2.1 expression 3; 2.8 ≦b≦ 3.1 expression 4; 2.7 ≦c≦ 3.1 expression 5; 3.8 ≦d≦ 4.2 expression 6.