Long‐Ultraviolet‐Excited White‐Light Emission in Rare‐Earth‐Activated Yttrium‐Oxyorthosilicate

White‐light emission was achieved by activating yttrium oxyorthosilicate with two rare‐earth elements, (Y 1− m − n Ce m Tb n ) 2 SiO 5 . Ce 3+ strongly absorbs at λ ex =358 nm and produces a broad, mainly blue emission with a tail that extends out to 600 nm (orange), and transfers energy efficiently to Tb 3+ , which produces strong green‐line emissions at 550 nm and some red emission around 650 nm. At λ e x =358 nm, chromaticity coordinates of the optimally activated (Y 0.9625 Ce 0.0075 Tb 0.03 ) 2 SiO 5 were found to be x =0.266, y =0.365 with a color temperature 8512 K. Upon mixing in another red‐emitting phosphor, (Y 0.955 Bi 0.005 Eu 0.04 ) 2 O 3 , the chromaticity and color rendering index values were improved.