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EFFECTS ON PRESSURE ON THE SPECTRA, LIFETIMES AND ENERGY TRANSFER OF Eu
P5O14, Tb P5O14 AND Eu1-xTbxP5O14
B. Blanzat, N. Tercier, J. Denis, C. Barthou
To cite this version:
B. Blanzat, N. Tercier, J. Denis, C. Barthou. EFFECTS ON PRESSURE ON THE SPECTRA,
LIFETIMES AND ENERGY TRANSFER OF Eu P5O14, Tb P5O14 AND Eu1-xTbxP5O14. Journal
de Physique Colloques, 1984, 45 (C8), pp.C8-71-C8-74. �10.1051/jphyscol:1984814�. �jpa-00224312�
JOURNAL DE PHYSIQUE
Colloque C8, suppl6rnent au nO1 1, Tome 45, novernbre 1984 page C8-71
EFFECTS ON PRESSURE ON THE SPECTRA, LIFETIMES AND ENERGY TRANSFER OF Eu P5Ol4# T b P5014 AND E u ~ - ~ T ~ ~ P5014
B. Blanzat, N. Tercier, J.P. Denis and C. Barthou
Labomtoire de Physico-Chimie ~ i n ~ m Z e + , EcoZe CentmZe des Arts et Ikznujactures, Grande Voie des Vignes, 92290 Chdtenay-MaZabry, France Rdsumd - L'effet de la pression sur la fluorescence des ions ~ b et Eu ~ + 3+
dans des cristaux mixtes Tb Eu P 0 est dtudid jusqu's 210 kbars. Un x 1-x 5 14
3+ 3+
fort transfert d'dnergie Tb -+ Eu est observe et on montre que l'effet de la pression sur ce transfert est gouvernd par une relaxation diffusion-limitd.
En utilisant la spectroscopie rdsolue dans le temps sous haute pression on trouve que ce transfert est plus rapide avec la pression.
Abstract - The effect of pressure (up to 210 kbars) on the fluorescence of Tb3+ and E U ~ + ions in the mixed single crystals Tbx Eul-x P5014 is investi- gated. A strong T b 3 + 4 E U ~ + energy transfer is observed and the pressure dependence of this transfer is shown to be governed by diffusion-limited relaxation. Using time-resolved spectroscopy under high pressure this energy transfer is found to be faster with pressure.
INTRODUCTION.
High pressure is a useful tool for probing material ~roperties. Through shifting ener- gy levels or changing transition probabili- ties, pressure has been shown to strongly affect the efficiency and kinetics of lu- minescence under high pressure leading to a better understanding of competing pro- cess.
Over the past ten years, the spectroscopic properties of stoechiometric laser mate- rials like rare earth pentaphosphates
(RE) P5OI4 is a topic of widespread inte- rest. The most important property of this class of materials is that they exhibit unusually weak concentration quenching and the physical mechanism for the quen- ching process is not very well understood at this time.
EXPERIMENTAL APPARATUS AND PROCEDURE.
Pressure measurements were made in a dia- mond anvil cell capable of reaching a maximum of 300 kbars. A schematic diagram of the steady state emission and decay apparatus is shown on fig. 1. The exciting light correspond to a selective excitation
5 3+
of the D 2 level of Eu (dye: rhodamin 6 6 )
PULSE G E N E R I I O R
511 Sm ROFlN 7\10
C ( W I " 0 L
PRINTER APPLE II
EPSON 11 EUROPL U S
t
Fig. 1 - Steady state, decay and time-resolved apparatus block diagram.
+ ERA 928 CNRS
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984814
JOURNAL DE PHYSIQUE
I
0 100 1 0 0 P ,,o,
Fig. 2 - Pressure dependence of the
7~ 1 sublevels of Eu 3+ . Fig. 3 - Effect of pressure on the lifetime of Eu 3+ .
or the 5 ~ 4 level of Tb 3+ (dye: coumarin 481).
EXPERIMENTAL RESULTS AND ANALYSIS.
The previous results (1) obtained from EPR, fluorescence and crystallographic wpe- riments permit concluding that the point symmetry of Eu 3+ in Eu P5014 is C at 1 bar.
As described by Huber et a1 (2) the decrease of the splitting between the two lower levels of the 7~ multiplet (fig. 2) indicates an approach toward a C site symme-
1 2v
try. The antilevel crossing of the two lower levels at 150 kbars is confirmed by li- fetime measurements of Eu 3+ (fig. 3). The observed increase in the fluorescence decay rate at high pressure in Lal-xE~x P5014 and Lal,xTbx P5014 could be due to an increa- se in the radiative decay rate and/or for an increase in the non-radiative decay rate of each Eu 3+ or l'b3+ ion since single-ion effects should be independent of concentra- tion (fig. 4).
On the other hand, after a selective excitation ion the 5 ~ 4 level of ~ b the decrea- ~ + se of the Eu3+ lifetime with pressure and concentration (fig. 5) may be interpreted by a weak back-transfer from E U ~ + to ~ b due to the overlapping of levels 5 ~ 4 ~ + of
l'b3' and 5 ~ 2 of Eu3+ with pressure. It will be eventually confirmed by the absorption
Fig. 4 - Evolution of the lifetimes of Eu 3+ Fig. 5 - Evolution of the and ~ b with concentration and high pressu- ~ + lifetimes of ~ u with con- ~ +
centration and high pressu- re in Tb Eu P 0
1-x x 5 14'
measurements under high pressure actually in pro- gress.
8 -. F l The classical Tb 3+ --FEU 3+ energy transfer is en-
rs,.,Eux Pso,G
hanced by high pressure (fig. 6) although of minor
I
importance than the concentration effect. At 1 bar
'1 the decay is logarithmic over most, if not all, of the time accessible to measurement. Because of the
1
,' t
fast diffusion, variation in the transfer times
21; t
" 1
for differents donor-acceptor pairs are effective-
5;.
$ j b o ,ly averaged out and the donor system exhibits a
',
I I O L D . .- - -
(15 L~~~
- simple exponential decay. At 110 and 175 kbars
I ; <
(fig. 7 - 8) the decay cfeviates from a simple ex-
!
-.
. & .... ponential dependence. The initial non exponential
.. .-...:. . portion of the decay is attributed to relaxation
I
1b(4, d2 C L Od EIP,o,~
3+
by direct ~ b ~ t + EU energy transfer. The final portions of the decays are exponential. Note that Fig, 6 - Evolution of the 3+
as the Eu concentration is decreased, the decay time of the exponential portion increases. This is lifetimes of ~ b with con- ~ +
characteristic of a diffusion-limited relaxation centration and high pressu-
mechanism since the average distance required for re in Tb E u ~ - ~ P5014.
X energy to migrate to a E U ~ + is increased. At 175 kbars the initial non exponential portion of the decay is increased.
The time-resolved spectroscopy results under pressure (fig. 9) clearly indicate that the ~ b ~ ' . 3u3+ energy transfer is more and more faster with increasing pressure but above about 150 kbars the E U ~ + luminescence intensity decreases as shown and descri- bed on fig. 5.
This work showing the efficiency of a energy migration mechanism in (Tb-Eu) P5014 with pressure backs up the conclusions (3) on Nd P5014 where the results are more consistent with a model of energy migration quenching that one of cross-relaxation.
. ..
..
. . Eut, rbon P,O,c-
Eum 1 bor P,O,,- '
2 1
".
', 0435n.
0.192-.
0 0.5 1 1.5 2
11me 1 m s l
