As a promising phosphor for fluorescent lamp

Ce-Mn activated fluo-rinphosphate(FAP:Ce

Mn) has been studied in these years. The lumen efficiency of this phosphor is very high

but one drawbacks of it is its low lumen maintenance in lamp. The depreciation rate of. FAP:Ce

Mn in lamp is about twice as much as that of Halophosphor ((F

Cl) AP:Sb

Mn). To improve the application of this phosphor

it is essential to study the depreciation properties of FAPCCe

Mn.In this paper

the depreciation of FAP:Ce

Mn both in lamp and under the UV radiation of (185+254) nm is reported

the key factors which affect phosphor depreciation are analyzed and possible mechanism of its depreciation is conjectured.The samples were prepared from solid state reaction. The 40W fluorescent lamps were made with ordinary technique and its lumen output in different operating time was measured. A 25W low pressure Hg discharge lamp was used as the source of UV radiation. Efficiency of samples in different radiation time was measured and the diffuse reflection spectra of samples were measured as well.Depreciation curves of lumen efficiency of FAP:Ce

Mn and (F

Cl) AP:Sb

Mn in fluorescenct lamps are shown in Fig.1. It can be seen that the depreciation processes of the two phosphors are very similar

but the depreciation rate of FAP:Ce

Mn is about twice as much as that of (F

Cl)AP:Sb

Mn.Depreciation curves of efficiency of FAP:Ce

Mn and (F

Cl)AP:Sb

Mn under UV radiation of 254nm are shown in Fig.2.It shows that the depreciation rate of FAP:Ce

Mn is about 3 times as much as that of (F

Cl)AP:Sb

Mn. Two main factors affect the depreciation properties of FAP:Ce

Mn particularly. Ce concentration and the atmosphere in which the sample isprepared

Fig. 3 and 4 show the effect of Ce concentration on the depreciation rate

and the absorption properties of the phosphor. The depreciation rate of FAP:Ce

Mn is almost directly proportional to the Ce concentration. And when Ce exists

the absorption of the sample in some wavelength areas markedly increases after UV radiation. Fig. 5 and Table 1 show the relationship between the forming atmosphere and depreciation of FAP:Ce

Mn.The sample prepared in reductive atmosphere is apt to depreciate and shows more intensive absorption in some areas after UV radiation than that made in air.According to the analysis by comparing the depreciation action between FAP:Ce

Mn and(F

Cl)AP.Sb

Mn both in lamp and under UV radiation

it can be concluded that the depriciation of the two phosphors belongs to the same

sort

caused by the formation of colour center in phosphor crystal by UV radiation.