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.