vii
TABLE OF CONTENTS
CHAPTER
TITLE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF FIGURES
xi
LIST OF TABLES
LIST OF ABBREVIATIONS
1
PAGE
xviii
xx
LIST OF SYMBOLS
xxii
LIST OF APPENDICES
xxiv
INTRODUCTION
1
1.1
Background of Study
1
1.2
Statement of Problem
4
1.3
Objectives of Study
5
1.4
Scope of Study
5
1.5
Significance of Study
6
viii
2
PHOSPHOR REVIEW
8
2.0
Introduction
8
2.1
Luminescence and Photoluminescence
8
2.1.1
Phosphorescence
10
2.1.2
Luminescence Mechanism
10
2.1.3
Fluorescence
2.1.4
2.2
2.3
2.4
2.5
3
and
Phosphorescence
Mechanism
13
Applications in Solid State Lighting
14
Light emitting diodes
17
2.2.1
19
White Light Emitting Diode
Phosphors
21
2.3.1
Developments of phosphors
22
2.3.2
Energy transfer and charge transfer
27
2.3.3
Concentration quenching effects
29
Design of phosphor
30
2.4.1
Host material
30
2.4.2
Activator
34
Phosphor synthesis
36
2.5.1
38
Solid state reaction
THEORIES OF STRUCTURAL AND OPTICAL
CHARACTERIZATIONS AND TECHNIQUES
41
3.0
Introduction
41
3.1
X-ray Diffraction Spectroscopy
41
ix
3.2
Fourier Transform Infrared Spectroscopy
45
3.3
Raman Spectroscopy
49
3.4
Scanning
3.5
Electron
Microscope
and
Energy
Dispersive X-ray
52
Photoluminescence Spectroscopy
55
3.5.1
Commission internationale de l'éclairage
(CIE) chromaticity coordinate
3.6
4
5
56
UV-Vis-NIR (UV-Vis) spectroscopy
60
3.6.1
62
Band gap estimation
PHOSPHOR
SYNTHESIS
AND
CHARACTERIZATION
64
4.0
Introduction
64
4.1
Phosphor Synthesis
64
4.2
Phosphor Characterizations
69
4.2.1
X-ray Diffraction (XRD)
69
4.2.2
Infrared Absorption Spectroscopy (FTIR)
71
4.2.3
RAMAN Spectroscopy
72
4.2.4
Scanning Electron Microscopy (SEM)
73
4.2.5
Energy Dispersive X-ray (EDX)
75
4.2.6
UV-Vis-NIR Spectroscopy
75
4.2.7
Photoluminescence Spectroscopy
76
STRUCTURAL STUDIES
78
5.0
Introduction
78
5.1
XRD Studies
78
x
6
5.2
IR absorption
5.3
RAMAN spectroscopy
103
5.4
Scanning Electron Microscope
115
5.5
EDX
119
5.6
Summary of structural analysis
124
OPTICAL PROPERTIES
126
6.0
Introduction
126
6.1
Optical absorption
126
6.1.1
134
6.2
6.3
7
92
Optical band gap estimation
Photoluminescence properties
142
6.2.1
Eu2+/ Eu3+ doped samples
142
6.2.2
Dy3+ doped samples
154
6.2.3
Eu2+/ Eu3+ and Dy3+ co-doped samples
157
Summary of optical analysis
170
CONCLUSIONS AND RECOMMENDATION
172
7.1
Summary of findings
172
7.2
Recommendation for future research
175
REFERENCES
APPENDICES A - D
177
201 - 213
xi
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
2.1
Configuration diagram of broad band emissions
12
2.2
Partial energy diagram of photoluminescence process
13
2.3
Cross section layout of (a) LED and (b) GaN LED
chips
2.4
18
Band gaps energy and equivalent wavelength of III-N
semiconductor
with
wurtzite
(α-phase)
and
zincoblende (β-phase) structure at 300 oK (Montanari
2005)
2.5
Energy transfer luminescence process in a phosphor
between sensitizer (S) and acceptor (A)
2.6
28
Microscopic atom arrangement of single crystal,
poly-crystal and amorphous solid
2.7
20
31
Microstructure of alumina ceramic under SEM
imaging (Shimai et al. 2013)
32
2.8
Illustration of diffusion process to produce SrSiO3
40
3.1
Basic layout of x-ray diffraction in atomic planes
43
3.2
Basic layout of Bragg-Brentano X-ray diffractometer
setup
43
xii
3.3
Examples of IR active vibrational modes (a)
symmetric stretching, (b) asymmetric stretching, (c)
rocking, (d) scissoring, (e) wagging and (d) twisting.
3.4
Schematic diagram of Michelson interferometer in
FTIR
3.5
Simplified
49
energy
mechanisms
of
level
infrared
diagram
showing
absorption,
Rayleigh
scattering and Raman sattering
3.6
52
Schematic diagram of electron beam and specimen
interaction and its interaction volume
3.8
50
Examples of Raman active vibrational modes (a) and
(b) symmetrical stretching (c) symmetrical bending
3.7
47
53
Various modes of electron and atom interaction
showing generation of (a) secondary electrons and
characteristics X-rays and (b) back scattered electrons
3.9
54
CIE 1931 2o standard observer color matching
function (International Commission on Illumination
2004)
58
3.10
CIE 1931 chromaticity diagram
60
4.1
Carbon powder for carbon monoxide atmosphere
layout
66
4.2
Sample synthesis and characterization flow diagram
67
4.3
X-ray Diffractometer (PANAlytical X’Pert PRO
MRD PW3040) in School of Physics, Universiti
Sains Malaysia
4.4
69
Infrared Absorption Spectrometer (Perkin Elmer
Frontier) in Department of Chemistry, Universiti
Teknologi Malaysia
71
xiii
4.5
RAMAN Spectroscopy (Horiba Jobin Yvon HR 800
UV) in School of Physics, Universiti Sains Malaysia
4.7
Modular Coating System (Quorum Q150R) in School
of Physics, Universiti Sains Malaysia
4.8
72
74
Scanning electron microscopy and energy dispersive
X-ray (Hitachi TM3000 Tabletop SEM) in Faculty of
Biosciences & Medical Engineering, Universiti
Teknologi Malaysia
4.9
74
UV-Vis-NIR spectrophotometer (Shimadzu UV3101PC) in Department of Physics, Universiti
Teknologi Malaysia
4.10
75
Photoluminescence spectrophotometer (JASCO FP8500) in Ibnu Sina Institute, Universiti Teknologi
Malaysia
76
5.1
XRD patterns of SBS-a series
79
5.2
XRD patterns of SBS-c series
80
5.3
Rietveld refinements of SBSED-c XRD diffraction
pattern
5.4
81
Graph of crystallite size against samples from SBS-a
and SBS-c series
5.5
82
Graph of unit cell volume against samples from SBSa and SBS-c series
5.6
Simulated
crystal
83
structure
of
SrB2Si2O8
and
BaB2Si2O8 viewed from (101), (110) and (011) plane.
86
5.7
XRD patterns of BBS-a series
87
5.8
XRD patterns of BBS-c series
88
xiv
5.9
Rietveld refinements of BBSED-c XRD diffraction
pattern
5.10
89
Graph of crystallite size against samples from BBS-a
and BBS-c series
5.11
90
Graph of unit cell volume against samples from BBSa and BBS-c series
5.12
91
FTIR spectra of SrB2Si2O8 phosphor specimens
sintered in air
5.13
93
FTIR spectra of SrB2Si2O8 phosphor specimens
sintered in CO
5.14
93
FTIR spectra of BaB2Si2O8 phosphor specimens
sintered in air
5.15
95
FTIR spectra of BaB2Si2O8 phosphor specimens
sintered in CO
95
5.16
Illustration of bonding in SrB2Si2O8 and BaB2Si2O8
100
5.17
FTIR spectra of SrB2Si2O8 against BaB2Si2O8
101
5.18
RAMAN spectra of air and CO sintered SBS samples
104
5.19
RAMAN spectra of air and CO sintered SBSED
samples
5.20
Modelled
105
danburite
rings
in
SrB2Si2O8
and
BaB2Si2O8
108
5.21
RAMAN spectra of air and CO sintered BBS samples
109
5.22
RAMAN spectra of air BBSD sample and CO
sintered BBSED samples
5.23
110
RAMAN spectra of SrB2Si2O8 against BaB2Si2O8 by
SBSED-c and BBSED-c sample comparison
114
xv
5.24
Low magnification SEM images of SBS samples
117
5.25
Low magnification SEM images of BBS samples
118
5.26
EDX spectra of SBS series sample sintered in air
atmosphere
5.27
EDX spectra of SBS series sample sintered in CO
atmosphere
5.28
129
Normalized diffused reflectance spectra of BBS-a
samples in UV-Vis-NIR region
6.4
127
Normalized diffused reflectance spectra of SBS-c
samples in UV-Vis-NIR region
6.3
123
Normalized diffused reflectance spectra of SBS-a
samples in UV-Vis-NIR region
6.2
122
EDX spectra of BBS series sample sintered in CO
atmosphere
6.1
121
EDX spectra of BBS series sample sintered in air
atmosphere
5.29
120
130
Normalized diffused reflectance spectra of BBS-c
samples in UV-Vis-NIR region
131
6.5
Kubelka-Munk function of SBS-a series samples
132
6.6
Kubelka-Munk function of SBS-c series samples
133
6.7
Kubelka-Munk function of BBS-a series samples
133
6.8
Kubelka-Munk function of BBS-c series samples
134
6.9
Linear regression fits of (F[r]hv)1/2 and (F[r]hv)2
against hv of sample SBS-a
6.10
135
([F(R)hv]2 versus hv plots of samples from SBS-a
series
136
xvi
6.11
([F(R)hv]2 versus hv plots of samples from SBS-c
series
6.12
([F(R)hv]2 versus hv plots of samples from BBS-a
series
6.13
145
Eu2+ emission and excitation schematic diagram in
SrB2Si2O8 host
6.19
143
De-convolution of Eu2+ 4f65d1 → 4f7 emission of
SBSE-a sample by using Gaussian fitting
6.18
143
Emission spectra of BBSE-a and BBSE-c excited at
390 nm
6.17
139
Emission spectra of SBSE-a and SBSE-c excited at
390 nm
6.16
137
Plots of band gap energy against doping condition
from all samples in each series
6.15
137
([F(R)hv]2 versus hv plots of samples from BBS-c
series
6.14
136
146
Excitation spectra of SBSE-a (λem = 437 nm), SBSE-c
(λem = 437 nm), BBSE-a (λem = 405 nm) and BBSE-c
(λem = 405 nm)
6.20
De-convolution of Eu3+ emissions of BBSE-a samples
using Gaussian fitting
6.21
151
Depicted transitions of Dy3+ and Eu3+ in BaB2Si2O8
phosphor.
6.23
150
Excitation spectra of SBSE-a, SBSE-c, BBSE-a and
BBSE-c (λem = 613 nm)
6.22
147
153
Emission spectra of SBSD-a, SBSD-c, BBSD-a and
BBSD-c recorded at 350 nm excitation
155
xvii
6.24
Excitation spectra of SBSD-a, SBSD-c, BBSD-a and
BBSD-c (λem = 575 nm)
6.25
Emission spectra of SBSED-a and SBSED-c (λex =
390 nm)
6.26
164
PL excitation spectra of BBSED-a and BBSED-c (λem
= 613 nm)
6.33
164
PL excitation spectra of BBSED-a and BBSED-c (λem
= 575 nm)
6.32
163
PL excitation spectra of BBSED-a and BBSED-c (λem
= 406 nm)
6.31
161
De-convolution of Eu3+ emissions of BBSED-a
samples using Gaussian fitting
6.30
160
PL emission spectra of BBSED-a and BBSED-c (λex
= 350 nm)
6.29
159
PL emission spectra of BBSED-a and BBSED-c (λex
= 390 nm)
6.28
157
Excitation spectra of SBSED-a and SBSED-c
recorded by observing 435 nm
6.27
156
165
Decay curves of (a) BBSD-a against BBSED-a (λem =
575 nm), (b) BBSD-c against BBSED-c (λem = 575
nm), (c) BBSE-a against BBSED-a (λem = 613 nm)
and (d) BBSE-c against BBSED-c (λem = 613 nm)
6.34
167
CIE coordinate of all phosphors plotted in CIE
chromaticity diagram with approximate color zone
and actual images of all phosphors under UV
excitation
168
xviii
LIST OF TABLES
TABLE NO.
2.1
TITLE
PAGE
Electromagnetic radiation wavelength and color
(Bruno and Svoronos 2005)
2.2
9
Overview of emission color, field of applications and
shortcomings of recently developed and important
phosphors
2.3
24
Emission color and ground state energy of commonly
used
phosphor
activators
(Xie
et
al.
2011,
Lakshmanan 2008)
35
4.1
List of compositions and notion for each sample
68
5.1
Crystallographic data of synthesized samples from
SBS series
82
5.2
Ionic radii of relevant atoms (Shannon 1976)
84
5.3
Crystallographic data of synthesized samples from
BBS series
5.4
89
FTIR vibrational band assignments for SBS and BBS
series
98
5.5
RAMAN band assignments
112
5.6
Summary of structural analysis
124
6.1
Optical band gaps of all specimens with allowed
direct band gap type
138
xix
6.2
Luminescence decay constant, τ of BBS samples
6.3
Summary of emission color and chromaticity
6.4
167
coordinate of all prepared phosphors
169
Summary of optical analysis
170
xx
LIST OF ABBREVIATIONS
BAM
-
BaMgAl10O17
BSE
-
Back scattered electrons
CIE
-
Commission International del’Eclairage
CO
-
Carbon Monoxide
COD
-
Crystallography Open Database
CRT
-
Cathode ray tube
CT
-
Charge transfer
CTB
-
Charge transfer band
DRS
-
Diffused reflectance spectra
EDX
-
Energy dispersive X-ray
et al.
-
et alia (and others)
etc.
-
et cetera (and other things)
FL
-
Fluorescent lamp
FT
-
Fourier transform
FTIR
-
Fourier transformed infrared
FHWM
-
Full width half maximum
GOF
-
Goodness-of-fit
HDTV
-
High definition television
HOMO
-
Highest occupied molecular orbital
xxi
ICDD
-
International Centre for Diffraction Data
IR
-
Infrared
KM
-
Kubelka-Munk
LCD
-
Liquid crystal display
LED
-
Light emitting diode
LUMO
-
Lowest unoccupied molecular orbital
MQW
-
Multiple quantum well
NBO
-
Non-bridging oxygen
NIR
-
Near-infrared
PDP
-
Plasma display panel
PL
-
Photoluminescence
RGB
-
Red/Green/Blue
SEM
-
Scanning electron microscope
SSL
-
Solid state lighting
TV
-
Television
UV
-
Ultraviolet
Vis
-
Visible
VUV
-
Deep ultraviolet
WLED
-
White light emitting diode
YAG
-
(Y,Ga)2Al5O12
xxii
LIST OF SYMBOLS
%T
-
Transmittance
µ
-
Reduced mass
ε
-
Absorptivity
ηT
-
energy transfer efficiency
θ
-
Diffracted angle
λ
-
Wavelength
χ2
-
Goodness of fit
A
-
Absorbance
a
-
Eu2O3 dopant concentration (mol%)
b
-
Dy2O3 dopant concentration (mol%)
c
-
Velocity of light
d
-
Spacing between planes
D
-
Diffusion coefficient
Do
-
Maximum diffusion coefficient at infinite temperature
E
-
Energy
EA
-
Activation energy for diffusion
h
-
Plank’s constant
I
-
Samples spectrum intensity
I(λ)
-
Spectral power distribution
xxiii
Io
-
Background spectrum intensity
Is
-
Peak intensity of the sensitizer in the presence of acceptor
Iso
-
Peak intensity of the sensitizer in the absence of acceptor
k
-
Force constant of a bond
l
-
Thickness
m
-
Mass
M
-
Sr or Ba
n
-
Integer value
R
-
Gas constant
-
Reflectance of an infinitely thick sample
S
-
Intensity ratio
T
-
Temperature
v
-
Frequency
x, y
-
chromaticity coordinate
-
standard observer color matching functions
, ,
X, Y, Z -
Tristimulus values
xxiv
LIST OF APPENDICES
APPENDIX
A
TITLE
Sample
composition
and
PAGE
stoichiometric
weight calculations
B
CIE
1931
2o
standard
201
observer
color
matching function in 1 nm interval
C
202
Standard NIST Si (SRM 640) scan with
FWHM, Gauss de-convoluted FWHM and
D
Lorentz de-convoluted FWHM fittings
211
List of publications
212