tb x z 0 3x can be regarded as equivalent by x ray analysis to the phosphor having z x and shows identical emission characteristics wherein x y z and x have the same meanings as defined above and x 39 is in a range of x to 0 3x are also included in the scope of the present invention the value of x is in a range of 0 001 to 0 95 as described above but a preferable range is 0 005 to 0 15 as the element represented by z lithium is preferable because it fails to form an amalgam with hg now the present invention will be described in detail referring to the following examples the following raw materials were blended or mixed sufficiently in a ball mill ______________________________________strontium carbonate srco sub 3 66 7 gmagnesium carbonate mgco sub 3 12 3 gsilicon dioxide sio sub 2 19 3 gterbium oxide tb sub 4 o sub 7 1 4 glithium carbonate li sub 2 co sub 3 0 3 g______________________________________ then the resulting mixture was filled in a quartz crucible and fired at 1300 u00b0 c for 3 hours in an argon gas atmosphere the resulting phosphor having the following chemical composition formula was excited under 253 7 nm radiation whereby an efficient green emission having emission spectra as shown in fig1 was obtained the excitation sources for the phosphor were not restricted to the 253 7 nm radiation when the excitation was made under.