LUMINESCENCE OF RE
OVERSATURATED CRYSTALS
A. Gektina*, N. Shirana, V. Nesterkinaa, G. Stryganyukb,
K. Shimamurac, E. Víllorac, K. Kitamurac
aInstitute
bHASYLAB
cAdvanced
for Scintillation Materials, NAS of Ukraine, Kharkov
at Deutsches Elektronensynchrotron DESY, Hamburg, Germany
Materials Lab., Nat. Inst. for Materials Science, Tsukuba, Japan
Motivation
 Fluorides allows to modify properties
Scintillator  phosphor  storage  dosimetry
 Broad variety of crystal lattices
What is the RE doping optimum?
LiF
cubic
BaF2
fluorite
ВаМgF4
orthorhombic
 LiF –
KMgF3(Eu) –
 BaFBr(Eu) –
 BaF2 –
 LiBaF3(Ce)–
dosimeter
 CaF2(Eu) –
scintillator
LiBaF3
perovskite
UV dosimeter
screen phosphor
fast scintillator
n/g discriminator
LiCaAlF6 / LiSrAlF6
colquiriite
New phosphors M1-xRExF2+x (M=Ca, Sr, Ba)
increase of RE3+ concentration in fluoride matrix
RE3+-Fi¯ dipole
~0.1%
dimer, trimer, etc.
~1-2%
detect
clusters
REF3 phase
~3-5%
Fi
M1-xRExF2+x
~10%
20-50%
VFc
{F12}
Structure of fluorite
MF2 (М=Ca, Sr, Ba)
Defect cluster
[RE6F36]
Supercluster
{M8[RE6F68-69]}
It is supposed that defect clusters and fluoride phases
of non-stoichiometric crystals can form nanostructures that opens
an possibility to engineering materials with various kinds of
properties.
Phase Diagrams of Ba0.65Pr0.35 F2.35 Systems
BaF2
BaF2–Pr (0.3 mol%)
*)
BaF2–Pr (3 mol%)
*)
BaF2–Pr (35 mol%)
BaF2–Pr (35mol%)  Ba0.65Pr0.35 F2.35
Internal structure is not still clear
but single crystals are available
*)Rodnyi, Phys.Rev. (2005)
RE oversaturated crystals
crystal
a, Å
CaF2
5.46305(8)
CaF0.65Eu0.35F2.35
5.55382(8)
CaF0.65Pr0.35F2.35
5.61359(4)
SrF2
5.800
Sr0.65Pr0.35F2.35
Me1–xPrxF2+x
5.81578(2)
BaF2
6.200
BaF0.65Pr0.35F2.35
6.03744(6)
Me1–xPrxF2+x
MeF2–Pr
PrF3
Which properties will dominates?
M= Ca,Sr,Ba 0.22 < x < 0.5
ion
R, Å
Ca2+
1.26
Eu3+
1.21
Pr3+
1.28
Sr2+
1.39
Ba2+
1.56
F–
1.19
Fluorides phase structure, superlattice
Non coherent inclusions
Coherent inclusions
M2+
R3+
nano phases
M1-xRxF2+x with R3+ to 40%
Gleiter, Acta Met. (2000)
Sobolev, Crystallography (2003)
Fluorides phase structure, superlattice
Non coherent inclusions
nano phases
Model of non stoichiometric
crystal with R3+ content 40%
Coherent inclusions
Coincidence lattice with R3+
content 42.86% (Ba4Yb3F17).
Other step is 15.38%
Sobolev, Crystallography (2003)
Eu2+ Eu3+ transformation by “lattice engineering”
CaF2(Eu) phosphor  Ca0.65Eu0.35 F2.35
Eu2+ emission
in CaF2(Eu)
Eu3+ emission
in Ca0.65Eu0.35 F2.35
CCD camera
sensitivity
1. At energies E < 6.5 eV only interconfigurational 4f-4f transitions are
observed;
2. Intraconfigurational 4f-5d and charge transfer (F–→Eu3+) transitions occur
in range of 6.5-10.5 eV;
BaF2–Pr photon cascade emission
Cascade emission:
1 step: 1S0 → 1I6 (~400 нм)
2 step: 3P0 → 3H4 (~482 нм)
45
3
BaPrF
E=7.75eV, T=8K
40
35
3
P0 H4
Second step only
Energy levels and Pr3+
transitions
3
10
3
3
P0 F2
3
P0 H5
15
3
5
3
20
P0 F4
3
P0 H6
25
3
Intensity, a.u.
30
BaF0.65Pr0.35F2.35
0
200
300
400
500
600
700
, nm
(Rodnyi, Phys.Rev., 2005)
Pr absorption in different hosts
Ca0.65Pr0.35F2.35
Sr0.65Pr0.35F2.35
Ba0.65Pr0.35F2.35
 Absorption peaks structure is similar
for different hosts
Clasters structure and Pr3+ excitation spectra
Excitation for
em= 250 нм
1. CaF2–Pr (0.1%)
2. Ca0.65Pr0.35F2.35
 Broad excitation spectra due to Pr3+
cluster structure and peaks
overlapping
300K
8K
(a)
Fig.6
Emission spectra
T=8 K
0
200
250
Ca0.65Pr0.35F2.35
1
350
400
1
2
3
4
5
6
450
SrF2:Pr(35%),
SrF2:Pr(35%),
SrF2:Pr(35%),
SrF2:Pr(35%),
SrF2:Pr(35%),
SrF2:Pr(35%),
500
550
600
650
E=5.04eV, T=8K
E=5.47eV, T=8K
E=5.85eV, T=8K
E=7.95eV, T=8K
E=6.89eV, T=8K
E=13.48eV, T=8K
700
750
(b)
Sr0.65Pr0.35F2.35
3+
Ce d-f
20
1
Fig.5
1
S0 I0
250
350
400
450
500
550
600
650
3
1000
750
(c)
3
3
3
100
3
3
3
P0 F2
3
3+
Ce d-f
Ba0.65Pr0.35F2.35
P0 F4
P0 H5
P0 H4
50
CaF2:Pr(35%); Em=402nm, Exc=5.79eV, T=300K
CaF2:Pr(35%); Em=402nm, Exc=6.20eV, T=300K
CaF2:Pr(35%); Em=402nm, Exc=6.78eV, T=300K
CaF2:Pr(35%); Em=402nm, Exc=8.00eV, T=300K
CaF2:Pr(35%); Em=402nm, Exc=9.18eV, T=300K
3
BaF2:Pr(35%), E=5.61eV, T=8K
BaF2:Pr(35%), E=7.75eV, T=8K
BaF2:Pr(35%), E=4.86eV, T=8K
700
3
1
2
3
300
P0 H6
0
200
100
E=5.39eV, T=8K
E=5.60eV, T=8K
E=5.80eV, T=8K
E=8.00eV, T=8K
E=13.48eV, T=8K
S0 D2
300
60
40
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
1
1
50
1
3
S0 F4
1
100
1
2
3
4
5
Counts
150
S0 G4
I, arb.u.
Emission spectra, 8K
0
200
250
300
350
400
450
500
Wavelength, nm
550
600
650
700
750
0
50
100
Time, ns
150
I, arb.u.
Emission spectra (photoexcitation), 300K
1
1
S0 I0
Fig.1
(a)
Emission spectra
T=300 K
1
2
3
4
5
6
E=9.92eV,
E=8.00eV,
E=6.70eV,
E=5.79eV,
E=5.70eV,
E=5.02eV,
Ca0.65Pr0.35F2.35
T=300K
T=300K
T=300K
T=300K
T=300K
T=300K
1
10
1
3
1
S0 H6
S0 D2
1
3
S0 F4
20
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
CaF2:Pr(35%),
1
1
S0 G4
30
0
200
250
300
350
400
450
500
550
600
650
Sr0.65Pr0.35F2.35
15
(b)
3+
Ce d-f
10
1
2
3
4
3+
Pr d-f
SrF2:Pr(35%), E=7.95eV, T=300K
SrF2:Pr(35%), E=6.70eV, T=300K
BaF2:Pr(35%), E=7.75eV, T=300K
BaF2:Pr(35%), E=5.17eV, T=300K
5
0
200
250
300
350
400
450
Wavelength, nm
500
550
600
650
Multi cluster structure
Decay curves for different cluster peak excitation
Ca0.65Pr0.35F2.35
g – luminescence and glow curve
CaPrF g-luminescence (1600V)
0,18
404
275
Intensity, a.u.
0,16
d-f
Pr
0,14
0,12
0,10
0,08
f-f
Pr
254
0,06
525
338
0,04
479
368
0,02 239
568
297
0,00
250
300
350
400
450
500
550
600
CaPrF
223 nm  to < 5 ns,
250 nm  t1 =25 ns and t2 =262 ns
273 nm  t1 =54 ns and t2 =300 ns
400 nm  t1 =71 ns and t=330 ns
Wavelength, nm
SrPrF N2 g-luminescence (1600V)
0,08
Pr
0,06
Ce-traces
0,04
Pr
405
0,02
248
317
489
345
0,00
300
400
500
600
SrPrF
230 and 275 nm  to <5 ns
325 nm  t1 =35 ns
400 nm  t1 =34 ns
475 nm  t1 =23 нс and t2 =139 ns.
Glow curve
3
10.01.2007 BaPrF-4 Послесвечение, доза 12*10 рад
Wavelength, nm
200
BaPrF
250 nm  to< 1 ns
325 nm  t1 =37 ns
480 nm  t2 =101 ns and t3 =549 ns
Intensity, a.u.
Intensity, a.u.
273
610
720
700
100
484
640
525
0
200
300
400
500
Wavelength, nm
600
700
800
Ca–Pr–F compound emission
Crystal
Properties
CaF2 :0.1%Pr
Ca0.65Pr0.35F2.35
PrF3
Structure
Cubic fluorite
Cubic fluorite
Lattice constant, Å
5.46305(8)
5.61359(4)
7.078 / 7.239
Coordination number
8
>8
9
233, 251, 272nm
―
482nm
233, 251, 272nm
400 nm
―
233, 251, 272nm
400 nm
―
233, 251, 272nm
―
482nm
233, 251, 272nm
400 nm
―
233, 251, 272nm
400 nm
―
154, 218
154, 218
223, 160 - 190
154, 218
223, 160 - 190
20
~3
11
330
~3
18
430
X-ray emission 77K
5d–4f, UV
1S -1I
o o
3P -3H
0
4
Photoluminescence Pr3+
5d–4f
1S -1I
o o
3P -3H
0
4
Excitation
of d f Pr3+ emission
C4v site
Cluster
τ1 (5d–4f), ns
τ2 (1S0 – 1I6), ns
Sr–Pr–F compound emission
Compound
SrF2-0.2%Pr
Sr0.65Pr0.35F2.35
PrF3
Structure
fluoride
fluoride
distorted
hexagonal
Lattice constant
a, Å
5.7996
5.81578(2)
7.078
7.239
Coordination
number
8
>8
9
233, 251, 272nm
―
482nm
233, 251, 272nm
400nm
482nm
233, 251, 272nm
400 nm
―
233, 251, 272nm
400 nm
482nm
233, 251, 272nm
400 nm
―
X-ray emission
5d–4f, UV
1S -1I
o o
3P -3H
0
4
Photoluminescence
5d–4f, UV
1S -1I
o o
3P -3H
0
4
233, 251, 272nm
―
482nm
Excitation of d f, nm
single Pr3+
154, 218
154, 218
154, 218
cluster
―
223, 160 −190
223, 160-190
25
―
<5
34
140
3, 18
430
―
Decay time
t1, (5d–4f)
t2, (1So-1Io)
t2, (3P0-3H4)
Photon cascade conditions
CaF2:Pr
0.2%
1.
S level should be separated from f-d level
2.
Minimal influence of cross relaxation
This has to corresponds to:
* coordination number more then 8-9
* large distance between Pr and anion ions
Ca0.65Pr0.35F2.35
Conclusions
1. Me1–xRExF2+x – is a stable crystal lattice with RE
content to 50%
2. RE ions aggregation gives a lot of clasters
3. Photon cascade emission is typical for all
Me0.65Pr0.35F2.35 compound but yield is still very low
4. Is it possible to make the same lattice with F
substitution by Cl, Br or I ?