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Submitted on 1 Jan 1987
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BROAD-BAND EMISSION OF Cr3+ IN MgAl2O4 SPINEL
W. Strek, P. Dere�, B. Jezowska-Trzebiatowska
To cite this version:
W. Strek, P. Dere�, B. Jezowska-Trzebiatowska. BROAD-BAND EMISSION OF Cr3+
IN MgAl2O4 SPINEL. Journal de Physique Colloques, 1987, 48 (C7), pp.C7-475-C7-477.
�10.1051/jphyscol:19877113�. �jpa-00226930�
JOURNAL DE PHYSIQUE
Colloque C7, supplement au n 9 1 2 , Tome 48, d6cembre 1987
BROAD-BAND EMISSION OF
cr3'
IN MgA12 O4 SPINELW . STREK, P. DERE& and B. JEZOWSKA-TRZEBIATOWSKA
Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 937, PL-53529 Wroclaw, Poland
A b s t r a c t .
The d o u b l e luminescence h e h a v i o u r of C r (111) i n s y n t h e t i c MgA1204 s p i n e l was o b s e r v e d . The n a t u r e o f s u c h a b e h a v i o u r i s i n v e s t i g a t e d by means t h e t i m e - r e s o l v e d luminescence s t u d i e s a t d i f f e r e n t e x c i - t a t i o n w a v e l e n g t h s . It i s shown t h a t t h e broad-rbroad e m i s s i o n ob- s e r v e d . i n s y n t h e t i c s p i n e l i s d u e t o t h e spin-allowed 4 ~ + 2
QAp
f l u o r e s c e n c e t r a n s i t i o n . I n t r o d u c t i o n
The C r (111) i o n o c c u p i e s a d i s t i n g u i s h e d p o s i t i o n o n a l i s t of l a s i n g i o n s . The d o u b l e f o r b i d d e n phosphorescence 2 E
-
4A2 was f o r t h e f i r s t t i m e u t i l i z e d f o r l a s e r o p e r a t i o n i n ruby. R e c e n t l y t h e s p i n a l - lowed '7T2-
4A2 f l u o r e s c e n c e was u t i l i z e d f o r t u n a b l e s o l i d s t a t e l a s e r s [ l - 2 1 . I t o c c u r s i n m a t e r i a l s c h a r a c t e r i z e d by low l i g a n d f i e l d Dq/B5
2 . 3.
I n t h i s p a p e r we r e p o r t t h e luminescence measurements o f C r (111) i n s y n t h e t i c MgA120,+ s p i n e l . We have found t h a t t h i s c r y s t a l i n c o n t r a s t t o t h e n a t u r a l s p i n e l [3
I
e x h i b i t s a broad band luminescence o r i g i n a t - i n g from t h e 4 ~ 2 s t a t e .R e s u l t s
The r e s u l t s of e a r l i e r works [ 4 , 5 ] on t h e o p t i c a l p r o p e r t i e s o f C r (111) i n s y n t h e t i c MgAl2O4 s p i n e l i n d i c a t e t h a t t h e C r (111) i o n
s u b s t i t u t e s two c r y s t a l l o g r a p h i c s i t e s i n t h i s c r y s t a l . The lumines- c e n c e s p e c t r a of C r (111) i n MgA1204 measured a t room t e m p e r a t u r e and
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19877113
C7-476 J O U R N A L DE PHYSIQUE
F i g . 1. Luminescence s p e c t r a o f C r (111) i n N.gA12011 a t 3 00 K . under d i f f e r e n t e x c i t a t i o n wavelengths a r e shown i n F i g . 1 .
One c a n n o t e t h a t t h e s p e c t r a r e c o r d e d f o r t h e e x c i t a t i o n wavelengths 607 and 51 4 nun shows r e m a r k a b l e d i f f e r e n c e s . The spectrum e x c i t e d by 514 nm ( t h i s l i n e e x c i t e s C r ( I I 1 ) i o n i n t h e s i t e B ) i s s i m i l a r t o t h e annealed n a t u r a l s p i n e l whereas t h e spectrum e x c i t e d by 607 nm ( t h i s l i n e i s a d j u s t e d t o e x c i t e t h e second s i t e A ) i s c h a r a c t e r i z e d by broad band e m i s s i o n c e n t e r e d a t 13 8 0 0 an-'. The s p e c t r u m e x c i t e d by 488 nrn combines t h e f e a t u r e s o f b o t h t h e former o n e s . To g e t i n s i g h t i n t o t h e n a t u r e of d o u b l e luminescence b e h a v i o u r o f C r (111) i n MgA1204 we h a ' ~ e performed t h e luminescence measurements up t o 600 K. The v a r i -
a t i o n of luminescence decay t i m e s w i t h t e m p e r a t u r e s i s shown i n F i g . 2 .
F i g . 2 . The t e m p e r a t u r e dependence of luminescent e decay t i m e s o f C r (111) i n MgA120h
.
We have observed t h a t t h e decay t i m e s combined w i t h broad band emis- s i o n w e r e 6 - 7 t i m e s s h o r t e r t h a n c o r r e s p o n d i n g t o narrow band emis- s i o n . The t i m e v a r i a t i o n o f luminescence s p e c t r u m e x c i t e d by 488 nun
( s e e F i g . 3 ) c l e a r l y i n d i c a t e s t h a t t h e broad band e m i s s i o n i s f a s t e r quenched t h a n t h e narrow band.
I n c o n c l u s i o n , t h e r e s u l t s p r e s e n t e d h e r e i n i n d i c a t e t h a t t h e d o u b l e luminescence b e h a v i o u r of C r (111) i n s y n t h e t i c MgA1204 s p i n e l i s ccnnbined w i t h two d i f f e r e n t C r (111) s i t e s . Whereas t h e C r (111) i n t h e s i t e s B g i v e s t h e spectrum s i m i l a r t o t h e n a t u r a l s p i n e l t h e C r (111) i n t h e i n v e r s e s i t e A g i v e s t h e broad band luminescence. T h i s s i t e i s c h a r a c t e r i z e d by lower l i g a n d f i e l d [ 5 ] , which p r e f e r s t h e 4 ~ 2
-
'A f l u o r e s c e n c e .2
P i g . 3 . Time - r e s o l v e d luminescence s p e c t r u m o f C r (111) i n MgA1204
.
R e f e r enc e s
1. J . C . W a l l i n g , O.G. P e t e r s o n , H.P. J e n s s e n , P.C. Morris and E.W. O t B e l l , IEEE J. Q u a n t . E l e c t r . QE 1 6 , 119, 1980.
2. J . Buchert and R.R. A l f a n o , L a s e r Focus, 919, 1189, 1980.
3 . D.L. W o d , G.F. Imbusch, R.M. McFarlane, P. K i s l u k and D.M. L a t k i n , J . Chem. Phys. 48, 52, 1969.
4 . H. van d e n Boom, A . J. J . v a n D i js s e l d o n k and J . C .M. Henning, J . Chern. Phys. 66, 2368, 1977.
5. W . S t r g k , P . Derefi a d B. Jeiowska-Trzebiatowska, s u b m i t t e d f o r p u b l i c a t i o n .
