We have synthesized phosphor by using a sealing vessel and evaluated its photoluminescence properties. The method using a sealing vessel is simple and economical in comparison with other methods reported up to date. As an activator concentration was increased from 0.1 mol% to 4 mol%, the main emission wavelength of the phosphor was increased from 642 nm to 651 nm due to the crystal field splitting of 5d levels of ion. Although the same amount of was used, the concentration of the activator ions, which were reduced from and substituted ions, was increased with increase of firing temperature. Therefore, the main emission wavelength was also. shifted from 645 nm to 651 nm with increase of firing temperature from . The critical distance() between ions calculated from the critical concentration was well matched with that() calculated from the Dexter formula.