Abstract
Emission, excitation and reflection spectra at various temperatures are studied. Under the C -band excitation, a simple emission band independent of the activator concentrations is observed for all the Ca(S: Se): Sn 2+ phosphors. As the fraction of CaSe is increased, the band-peak (545 mµ for CaS: Sn 2+ at 77 K) shifts constantly towards shorter wavelengths and finally reaches 518 mµ in CaSe: Sn 2+ at 77K. In the excitation spectra, the curves characteristic of the Tl + -type ion center in the O h crystal field can be obtained for all the Ca(S: Se): Sn 2+ phosphors. The peaks of the C , B and A excitation bands are found at 311, 332 and 364 mµ for CaS: Sn 2+ , and at 327, 344 and 373 mµ for CaSe: Sn 2+ at 77 K. For all the Ca(S: Se): Sn 2+ phosphors, two additional excitation bands (409 and 448 mµ for CaSe: Sn at 77 K) are observed in the longer wavelength region of the A band at low temperatures.
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