luminescence of re oversaturated crystals a. gektin a *, n. shiran a, v. nesterkina a, g. stryganyuk...
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![Page 1: LUMINESCENCE OF RE OVERSATURATED CRYSTALS A. Gektin a *, N. Shiran a, V. Nesterkina a, G. Stryganyuk b, K. Shimamura c, E. Víllora c, K. Kitamura c a Institute](https://reader036.vdocuments.us/reader036/viewer/2022062408/56649f115503460f94c24932/html5/thumbnails/1.jpg)
LUMINESCENCE OF RE LUMINESCENCE OF RE
OVERSATURATED CRYSTALSOVERSATURATED CRYSTALS
A. Gektina*, N. Shirana, V. Nesterkinaa, G. Stryganyukb,K. Shimamurac, E. Víllorac, K. Kitamurac
aInstitute for Scintillation Materials, NAS of Ukraine, Kharkov
bHASYLAB at Deutsches Elektronensynchrotron DESY, Hamburg, Germany
cAdvanced Materials Lab., Nat. Inst. for Materials Science, Tsukuba, Japan
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Fluorides allows to modify propertiesScintillator phosphor storage dosimetry
Broad variety of crystal lattices
What is the RE doping optimum?
Motivation
LiCaAlFLiCaAlF66 / LiSrAlFLiSrAlF66
colquiriite LiBaFLiBaF33
perovskiteВаМВаМgFgF44
orthorhombicorthorhombicLiFLiF
cubicBaF2
fluorite
LiF – dosimeterKMgF3(Eu) – UV dosimeter
BaFBr(Eu) – screen phosphor
BaF2 – fast scintillator
LiBaF3(Ce)–
n/discriminator
CaF2(Eu) – scintillator
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New phosphors M1-xRExF2+x (M=Ca, Sr, Ba)
Structure of fluoriteMF2 (М=Ca, Sr, Ba)
Fi VFc
{F12}
Defect cluster[RE6F36]
Supercluster{M8[RE6F68-69]}
RE3+-Fi¯ dipole dimer, trimer, etc.
M1-xRExF2+xREF3
phase
increase of RE3+ concentration in fluoride matrix
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.
detect clusters
~0.1% ~1-2% ~3-5% ~10% 20-50%
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Phase Diagrams of Ba0.65Pr0.35 F2.35 Systems
Internal structure is not still clearbut single crystals are available
*)Rodnyi, Phys.Rev. (2005)
BaF2
BaF2–Pr (0.3 mol%) *)
BaF2–Pr (3 mol%) *)
BaF2–Pr (35 mol%)
BaF2–Pr (35mol%) Ba0.65Pr0.35 F2.35
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RE oversaturated crystals
Which properties will dominates?
crystal a, ÅCaF2 5.46305(8)
CaF0.65Eu0.35F2.35 5.55382(8)
CaF0.65Pr0.35F2.35 5.61359(4)
SrF2 5.800
Sr0.65Pr0.35F2.355.81578(2)
BaF2 6.200
BaF0.65Pr0.35F2.35 6.03744(6)
Me1–xPrxF2+x
M= Ca,Sr,Ba 0.22 < x < 0.5
ion R, ÅCa2+ 1.26
Eu3+ 1.21
Pr3+ 1.28
Sr2+ 1.39
Ba2+ 1.56
F– 1.19
Me1–xPrxF2+x
MeF2–Pr PrF3
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Fluorides phase structure, superlattice
Non coherent inclusions
nano phases
Gleiter, Acta Met. (2000)
Coherent inclusions
M2+
R3+
Sobolev, Crystallography (2003)
M1-xRxF2+x with R3+ to 40%
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Fluorides phase structure, superlattice
Non coherent inclusions Coherent inclusions
nano phases
Coincidence lattice with R3+ content 42.86% (Ba4Yb3F17).
Other step is 15.38%
Sobolev, Crystallography (2003)
Model of non stoichiometric crystal with R3+ content 40%
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Eu2+ Eu3+ transformation by “lattice engineering”
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;
CaF2(Eu) phosphor Ca0.65Eu0.35 F2.35
Eu2+ emissionin CaF2(Eu)
Eu3+ emissionin Ca0.65Eu0.35 F2.35
CCD camera sensitivity
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BaF2–Pr photon cascade emission
Cascade emission:
1 step: 1S0 → 1I6 (~400 нм)
2 step: 3P0 → 3H4 (~482 нм)
Second step only
Energy levels and Pr3+
transitions
(Rodnyi, Phys.Rev., 2005)
BaF0.65Pr0.35F2.35
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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
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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
300K8K
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Emission spectra, 8K
0 50 100 150
100
1000
Fig.5
Coun
ts
Time, ns
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
200 250 300 350 400 450 500 550 600 650 700 7500
50
100
3P
0
3F
4
3P
0
3F
2
3P
0
3H
6
3P
0
3H
5
3P03H
4
(c)
1 BaF2:Pr(35%), E=5.61eV, T=8K2 BaF2:Pr(35%), E=7.75eV, T=8K3 BaF2:Pr(35%), E=4.86eV, T=8K
Wavelength, nm
200 250 300 350 400 450 500 550 600 650 700 7500
50
100
150
1S
0
3F
4
1S
0
1G
4
1S
0
1D
2
1S01I
0
(a)
1 CaF2:Pr(35%), E=5.39eV, T=8K2 CaF2:Pr(35%), E=5.60eV, T=8K3 CaF2:Pr(35%), E=5.80eV, T=8K4 CaF2:Pr(35%), E=8.00eV, T=8K5 CaF2:Pr(35%), E=13.48eV, T=8K
I, a
rb.u
.
Fig.6Emission spectraT=8 K
200 250 300 350 400 450 500 550 600 650 700 7500
20
40
60
Ce3+d-f
Ce3+d-f
(b)1 SrF2:Pr(35%), E=5.04eV, T=8K2 SrF2:Pr(35%), E=5.47eV, T=8K3 SrF2:Pr(35%), E=5.85eV, T=8K4 SrF2:Pr(35%), E=7.95eV, T=8K5 SrF2:Pr(35%), E=6.89eV, T=8K6 SrF2:Pr(35%), E=13.48eV, T=8K
Ca0.65Pr0.35F2.35
Sr0.65Pr0.35F2.35
Ba0.65Pr0.35F2.35
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Emission spectra (photoexcitation), 300K
Ca0.65Pr0.35F2.35
Sr0.65Pr0.35F2.35
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Multi cluster structure
Decay curves for different cluster peak excitation
Ca0.65Pr0.35F2.35
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– luminescence and glow curve
CaPrF223 nm o < 5 ns,250 nm 1 =25 ns and 2 =262 ns 273 nm 1 =54 ns and 2 =300 ns 400 nm 1 =71 ns and =330 ns
SrPrF230 and 275 nm o <5 ns 325 nm 1 =35 ns 400 nm 1 =34 ns 475 nm 1 =23 нс and 2 =139 ns.
BaPrF250 nm o< 1 ns 325 nm 1 =37 ns
480 nm 2 =101 ns and 3 =549 ns
Glow curve
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PropertiesCrystal
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
X-ray emission 77K
5d–4f, UV1So-
1Io
3P0-3H4
233, 251, 272nm―482nm
233, 251, 272nm400 nm―
233, 251, 272nm400 nm―
Photoluminescence Pr3+
5d–4f1So-
1Io
3P0-3H4
233, 251, 272nm―482nm
233, 251, 272nm400 nm―
233, 251, 272nm400 nm―
Excitation of d f Pr3+ emission
C4v site 154, 218 154, 218223, 160 - 190
154, 218223, 160 - 190
Cluster
τ1 (5d–4f), ns
τ2 (1S0 –
1I6), ns
20 ~311330
~318430
Ca–Pr–F compound emission
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Compound SrF2-0.2%Pr Sr0.65Pr0.35F2.35 PrF3
Structure fluoride fluoride
distorted
hexagonal
Lattice constant a, Å
5.7996 5.81578(2) 7.0787.239
Coordination number
8 >8 9
X-ray emission
5d–4f, UV1So-
1Io
3P0-3H4
233, 251, 272nm―482nm
233, 251, 272nm400nm482nm
233, 251, 272nm400 nm―
Photoluminescence
5d–4f, UV1So-
1Io
3P0-3H4
233, 251, 272nm―482nm
233, 251, 272nm400 nm482nm
233, 251, 272nm400 nm―
Excitation of d f, nm
single Pr3+ 154, 218 154, 218 154, 218
cluster ― 223, 160 −190 223, 160-190
Decay time
1, (5d–4f)
2, (1So-
1Io)
2, (3P0-
3H4)
25―
< 534140
3, 18430―
Sr–Pr–F compound emission
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Photon cascade conditions
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
CaF2:Pr 0.2% Ca0.65Pr0.35F2.35
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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 ?