A yttrium silicate based phosphor and a method for synthesizing the phosphor by surface coating. The yttrium silicate based phosphor is synthesized by surface coating a Y.sub.2 SiO.sub.5 :Tb phosphor coated with a strontium (Sr)-thiogallate phosphor. In the method, Ga(NO.sub.3).sub.3, Eu(NO.sub.3).sub.3 and SrCO.sub.3 are mixed and stirred until the SrCO.sub.3 is completely dissolved. Next, a Y.sub.2 SiO.sub.5 :Tb phosphor is added to the mixture, and a sodium hydroxide (NaOH) is added to the mixture containing the Y.sub.2 SiO.sub.5 :Tb to adjust pH. Then, sulfur (S) is added to the pH-adjusted mixture. The sulfur containing mixture is dried, sieved, and fired at 750.degree. C. for 4 hours.
