Phosphor for down converting ultraviolet light of LEDs to blue-green light

A traffic signal, comprising:

• a housing;
• at least one lens;
• a radiation source having a peak emission wavelength of 420 nm and below;
• and
• a luminescent material having emission CIE color coordinates located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:
• a) x=0.000 and y=0.506;
• b) x=0.224 and y=0.389;
• c) x=0.280 and y=0.45;
• and
• d) x=0.000 and y=0.730.

A method of making a blue-green light illumination system, comprising:

• mixing a plurality of starting powders to form a starting powder mixture;
• firing the starting powder mixture to form a calcined-body;
• converting the calcined body into a phosphor powder having emission CIE color coordinates located within an area of a pentagon on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:
• e) x=0.0137 and y=0.4831;
• b) x=0.2240 and y=0.3890;
• c) x=0.2800 and y=0.4500;
• g) x=0.2879 and y=0.5196;
• and
• h) x=0.0108 and y=0.7220;
• placing the phosphor powder into the illumination system;
• and placing a light emitting diode into the illumination system.