LUMINESCENCE OF RE OVERSATURATED LUMINESCENCE OF RE OVERSATURATED CRYSTALS CRYSTALS A . Gektin a *, N. Shiran a , V. Nesterkina a , G. Stryganyuk b , K. Shimamura c , E. Víllora c , K. Kitamura c a Institute for Scintillation Materials, NAS of Ukraine, Kharkov b HASYLAB at Deutsches Elektronensynchrotron DESY, Hamburg, Germany c Advanced Materials Lab., Nat. Inst. for Materials Science, Tsukuba, Japan
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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.
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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
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
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%
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
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
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%
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%
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
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
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