Journal of Luminescence 40&41 (1988) 163 164 North-Holland, Amsterdam
LUMINESCENCE OF CERIUM (3+) ACTIVATED RARE EARTH SILICOPHOSPHATES
Zhupo HIJANG and Guoling MA Department
of Chemistry, Peking University, Beijing 100871, China
1. INTRODUCTION 3~ Terashima et al had ever reported that Th and Ce3~coactivated Lanthanum silicophosphates were good lamp phosphors1.
The emission, excitation and diffusive re— flectance spectra of Ce3~—activated LSP and GSP are shown in Fig.
Rare earth silicopho—
sphates with a general formula RE 203O.lOSiO2~
O.95P205 (RE represents La or Gd and these for— mula are simplified as LSP or GSP respectively) were synthesized terials
for making phosphors.
as good host ma— A systematic
vestigations on silicophoAphates the luminescence of properties 3~—activated lanthanum of and Ce gadolinium are reported.
2. RESULTS AND DISCUSSION Samples of definite composition and single phase were prepared by solid state reactions. Their crystal structure were determined by x—ray diffractometer
l5OmA) to be mono—
clinic and isostructural
1~i0200 214.0 280
with GdPO 6 (ASTM 26—660).
The lattice parameters were calculated, and are shown in Table
FIGURE 1 Emission spectrum (A 254nm)(a), diffusive reflectance and excitagon spectrum (A 320nm)(b)
TABLE 1. The lattice parameters of LSP and GSP
Their emission spectra consistdifference of a broadof band of two peaks with an energy 2000cm , corresponding to the transitions from excited Sd level to 4f 2F
3) parameters lattice a($.)
2F 3~. 712 and 512 of Ce There are two absorption bands in their excitation and diffusive reflectance spectra. The smaller band arisesfrom the host absorption and
samples were measured with a fluorescence spectra— meter type Hitachi
from the 4f——5d transition.
It shows that these
850. two compounds
Project Supported by National Natural Science Foundation of China.
0022 2313/88/$03.50 ~ Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
are highly efficient photolumine—
Z. Huang, G. Ma
(3 +) activated rare earth srl,cophosphates
scence phosphors. The optimum concentrations 3~doped in the LSP and GSP are 0.2 and 0.6 of Ce mole% respectively. We have found
shift of sub—level2
7/2 in the emission
spectrum of LSP:Ce3~ and GSP:Ce3~. Fig. 2 shows that the peak wavelength of Sd —2F 712 transition of LSP:Ce
at 298K shifts ca. 5nm toward short
wavelength from that at 77K.
WAVELENGTH( nm) FIGURE 3~ in3 the LSP at different Emission temperatures spectra 293K,of 388K Ce and 423K.
of the former decreases ca. 27% from 298K to 513K,
whereas that of the latter decreases ca.
to Dexter’s theory3, preliminary 3+ study on concentration quenching of Ce ions in these phosphors has been made.
From the con-
centration dependence relationship of the emission intensity lgx—lgI/x were experimentally
220 300 380 WAVELENGTH(nm)
We would consider that the concentra—
tion quenching of Ce3~ ions in these phosphors arises from the dipole—dipole interactions.
FIGURE 2 3+ Emission spectra of Ce in (La Ce ) 0 0.lSiO ~O.95P 0 at 77K and 293~8 0.2 2 3 2 2 ~ The temperature dependence of peak wavelength 2 — ~7I2 emission from 298K to 423K shows
the same trend (Fig.
3) as from 77K to 298K,
that is it shifts to short wavelength a little,
whereas the peak wavelength of Sd _2F 5/2 emission does not change as the temperature is varied
in the range of 77—298K and of 298—423K.
This means that
of Sd 2F and 712 moves
remain unchanged, meanwhile that of
apart from Sd level as the temperature is raised. 3+ emissions The temperature of Ce from transitions of quenching 5d _2F 2F 5/2 and Sd _ behave differently.
7/2 also intensity
REFERENCES 1. K. Terashima, Y. Kimura and K.Kohmoto, Toshib~ Review, 37 (1982) 110—111. 2. Xu Ti—sun, Song Zeng—fu, Acta Physica Sinica, 35 (1986) 213. 3. D.C. Dexter, J. Chem. Phys.
21 (1953) 836.