LUMINESCENCE PROPERTIES OPTIMISATION OF PRASEODIUM IN CaTiO3
P. T. Diallo, P. Boutinaud, R. Mahiou et J. C. Cousseins
Laboratoire des Matériaux Inorganiques et E.N.S.C.C.F.ESA-6002, Université Blaise Pascal - Clermont-Ferrand II63177 Aubière Cedex - France
LMI-ESA 6002
INTRODUCTION
The LuminophoreHost Matrix Activator
CaTiO3 Pr3+
- Chemistry under control (solid state chemistry, Sol-Gel)
- Easy to process (Films)
- Low band gap energy (< 4 eV)
→ Intense UV absorption BV → BC Beneficial to excite the activator.
→ Envisioned applications photoluminescence and cathodoluminescence.
1S0
3P0
1D2
1G4
3H4
UV
BLEU
ROUGE
IR
“Laser”
(S. S. Chadha, D. W. Smith, A. Vecht et C. S. Gibbons, SID 94 DIGEST, (1994), 51 -52)
y
x
Y2O3 : Eu3+CaTiO3 : Pr3+
- Chromatic coordinates (CIE)
CaTiO3 : Pr3+
Y2O3 : Eu3+
Red “Ideal” (NTSC)
Advantages of CaTiO3 : Pr3+ : Contrast increase in the red at lowenergetic cost (CaO, TiO2, Pr3+ not expensive).
Problem to be solved : - Determine luminescence mechanisms- Increase emission yield
x = 0,68y = 0,31
x = 0,65y = 0,35
x = 0,67y = 0,33
PROPERTIES AND MECHANISMS OF LUMINESCENCE OF CaTiO3 : Pr3+
CaTiO3 : Pr3+ : Polyvalent activator
λ (nm)
350 450 550 650300250200150
4f5d
Conduction band
I (u.a.)
λ (nm)
Excitation Emission
613
CaTiO3 : Pr3+
BV
BC
3,62 eV
4f5d
3H4
1D2
3P0
EnergyTransfer
Luminescence mechanisms of CaTiO3 : Pr3+
CaZrO3 : Pr3+
(G. Blasse et H. E. Hœfdraad , Phys. Stat. Sol. (a) 29 , (1975), K95-K97)
Pr- 4f5d
Energy
∆r3H4
1D2
3P0
450 500 550 600 650 λ (nm)
I (u.a.) 3P0 → 3H4
1D2 → 3H4
350 450 550 650 λ (nm)
1D2 → 3H4 Red
CaTiO3 : Pr3+
∆r3H4
10
20
ENERGY(x103 cm-1)
30
1D2
3P04f5d
IMPROVING LUMINESCENCE YIELD
1- Charge Compensation
Ca2+1-x Pr3+
xTi4+ O3 Not compensate→ Ca2+1-x Pr3+
xTi4+1-xTi3+
xO3
Ca2+1-2x Pr3+
x Na+x Ti4+ O3 → (2Ca2+ → 1Pr3+ + 1Na+)
Ca2+1-2x Pr3+
x Ag+x Ti4+ O3 → (2Ca2+ → 1Pr3+ + 1Ag+)
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3 →(1Ca2++1Ti4+→ 1Pr3++1Al3+)
Ca2+1-3x/2 (!)x/2 Pr3+
x Ti4+ O3 → Lacunar Perovskite
Solid State Reaction : T = 1200 °C , 4 hours / Air
Variation of the intensity of the Redemission
Ca2+1-x Pr3+
xTi4+ O3(Not compensate)
Ca2+1-2x Pr3+
x Ag+x Ti4+ O3 (gain 60%)
Ca2+1-2x Pr3+
x Na+x Ti4+ O3 (gain 30%)
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3 (gain 120%)
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3 (gain 150%)
x mole % Pr3+ 0 1 2 3 4 5 6
Relative Intensity (u.a.)
Exc. : 345 nmT = 300 K
0,2 %0
2
4
6
2- Sol-Gel method
IMPROVING LUMINESCENCE YIELD
N2
T = 60 °C
Agitator
Thermometer
Reactor
Acid Sol-gel
(pH = 3, solvent methanol)
(1-x)CaO + xPrCl3.7H2O + Ti(OC3H7)4
→ Ca1-xPrxTiO3 + 4C3H7OH
Basic Sol-gel
(pH = 10, solvent isopropanol)
(1-x)CaCl2.2H2O + xPrCl3.7H2O + Ti(OC3H7)4
→ Ca1-xPrxTiO3 + 4C3H7OH
Crystallization
Crystalline phase of interest formed above 760 °C
750 800 900 1000 1100 120060
70
80
90
100
Inte
nsi
ty (%
)
Crystallization temperature (°C)
(1 0 1)
10 20 30 40 50 60 70 80
2 theta (degree)
I (u.a.)
X rays Diagram(Anode Cu)
(1 0 1)
Morphologie
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3
T = 760 °C
5 µm
T = 1000 °C
5 µm
T = 1200 °C
5 µm
T = 760 °C
5 µm
T = 1000 °C
5 µm
T = 1200 °C
5 µm
Variation of Red Luminescence
800 900 1000 1100 1200
0
20
40
60
80
100R
elat
ive
Inte
nsit
y (%
)
Crystallization temperature (° C)
I Lum. = f(Crystallization Temperature)
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3
Luminescence properties optimization ofpraseodymium doped CaTiO3
Ca2+1-x Pr3+
xTi4+ O3(Not compensate)
Rel
ativ
e In
tens
ity
(u.a
.)
Exc. : 345 nmT = 300 K
Ca2+1-2x Pr3+
x Ag+x Ti4+ O3 (gain 60%)
Ca2+1-2x Pr3+
x Na+x Ti4+ O3 (gain 30%)
x mole % Pr3+ 0 1 2 3 4 5 6
0,2 %0
2
4
6 Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3 (gain 120%)
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3 (gain 150%)
8
10
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3 (gain 153%)
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3 (gain 160%)
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3 (gain 197%)
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3 (gain 261%) BasicSol-Gel1200 °C/4h
AcidSol-Gel1200 °C/4h
Ca2+1-x Pr3+
x Ti4+ 1-x Al3+
x O3
Ca2+1-3x/2 (!) x/2 Pr3+
x Ti4+ O3
Solid State1200 °C/4h
2 µm 2 µm
2 µm 2 µm
CONCLUSIONS
- Basic Sol-Gel Synthesis- Crystallization state- Materials densification
Red luminescence Intensity Increases
Ca0,997Pr0,002TiO3 Prepared by Sol-Gel methodunder basic conditions and heat treated at 1200 °C is a promising polyvalent Red luminophore.