CaS:Cu phosphors were prepared and their luminescence properties were studied. Copper is proved to be existed as monovalence in calcium sulphide from X-ray photoelectron spectra. In excitation spectra of CaS:Cu phosphors

three peaks have been observed. The peaks locate at 268nm

307nm and 400nm respectively.The peak of 268nm is overlapped between the excited state

1

T

2

(37700cm

-1

) of Cu

+

ions and the absorption edge of calcium sulphide

The peak of 307nm is caused by the excited state

1

E(32500cm-1) of Cu+ ions. The peak of 400nm is produced by the transformation process of Cu

+

→Cu

2+

e.