Synthesis and properties of undoped and transition metal (Mn2+, Cr3+) doped Zn2Sio4 and zn2snO4 phosphors

MINISTRY OF EDUCATION AND TRAINING 
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY 
LE THI THAO VIEN 
Synthesis and properties of undoped and transition 
metal (Mn2+, Cr3+) doped Zn2SiO4 
 and Zn2SnO4 phosphors 
DOCTORAL DISSERTATION ON MATERIAL SCIENCES 
HANOI – 2020 
MINISTRY OF EDUCATION AND TRAINING 
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY 
LE THI THAO VIEN 
Synthesis and properties of undoped and transition 
metal (Mn2+, Cr3+) doped Zn2SiO4 
 and Zn2SnO4 phosphors 
 Majors: Material Sciences 
 Code: 9440122 
DOCTORAL DISSERTATION ON MATERIAL SCIENCES 
 ADVISORS: 
1. Prof. Dr. PHAM THANH HUY 
2. Dr. NGUYEN THI KHOI 
HANOI – 2020 
 i 
COPYRIGHT DECLARATION 
This thesis compresses only my research results. It does not contain any previous 
data submitted by any people or organizations except that have been marked in the 
references. 
 Hanoi, 15/9/2020 
 Advisors PhD. Student 
Prof. Dr. Pham Thanh Huy Le Thi Thao Vien 
 ii 
ACKNOWLEDGEMENTS 
Although my name is on the cover of this dissertation, many people were of 
great importance to this research. I want to take a moment to extend my gratitude to 
the involved. 
The first, I would like to express my sincerest thanks to my supervisor, Prof. 
Pham Thanh Huy, excellence and estimable teacher, for all of his supports. His 
dedication to science has been encouraging me so much, protected me from the 
confusion since I started studying and researching at the Advanced Institute for 
Science Technology (AIST). 
This dissertation was carried out at AIST, together with several research groups 
researches. I had garnered variable information from these seminars with free 
discussions coming from all of our group members. Possibly just as important as the 
practical aid was the friendly, cooperative atmosphere at AIST; it made me enjoy 
virtually every second of working on my dissertation. I wish to thank Associate prof. 
Dao Xuan Viet; Dr. Nguyen Tu; Dr. Nguyen Duy Hung, and all of my teammates for 
their friendships with kind-hearts and unconditional assistance. 
The last few months weren’t easy, and I want to thank all my dearest friends, 
who helped me get back on track when I lost my laptop and found many difficulties 
in life. Without your care, understanding, and motivational speeches, this thesis 
would no doubt look different and not for the better. Your friendship makes me 
realize what a lucky person I am. 
For the last, more than I can say, I would like to express manifest thanks to my 
husband and two children for always being by my side, putting their truth in me 
during my duration at AIST. 
Lastly, I want to mention my father, mother, my parents-in-law, and two sisters, 
and thank them for making me the person that I have become. 
 Le Thi Thao Vien 
 iii 
CONTENTS 
LIST OF FIGURES ............................................................................................. viii 
LIST OF TABLES.... .......................................................................................... xiv 
BRIEF INTRODUCTION ...................................................................................... 1 
Chapter 1. INTRODUCTION ................................................................................ 8 
1.1. Background of Luminescence .............................................................. 8 
1.1.1. Luminescence .......................................................................................... 8 
1.1.2. Optical quenching .................................................................................... 9 
1.1.3. Electroluminescence................................................................................ 9 
1.1.4. Thermoluminescence ............................................................................ 10 
1.2. Background of Transition Metal (TM) ions in the crystal field10 
1.2.1. Transition metals10 
1.2.2. The effect of crystal fields on the separation of TM ions 11 
1.2.3. Tanabe-Sugano diagrams ...................................................................... 15 
1.2.4. Energy levels of Mn2+ ion in a crystal field .......................................... 18 
1.2.5. Energy levels of Cr3+ ion in a crystal field ............................................ 20 
1.3. Literature review of transition metal (Mn2+, Cr3+) doped Zn2SiO4 and 
Zn2SnO4 phosphors ....................................................................................22 
1.3.1. Structure and optical properties of Zn2SiO4: Mn2+.. 22 
1.3.2. Structure and optical properties of Zn2SnO4, Zn2SnO4:Mn2+ 
 24 
1.4. Phosphor-based LEDs ........................................................................26 
1.4.1. LED ....................................................................................................... 26 
1.4.2. Phosphor-based LEDs ........................................................................... 27 
1.4.3. LED application in agricultural lighting ............................................... 30 
Chapter 2. EXPERIMENTAL TECHNICS ......................................................... 32 
2.1. Introduction .......................................................................................32 
2.2. Synthesis of Zn2SiO4, Zn2SiO4:Mn2+, Zn2SnO4, Zn2SnO4:Mn2+, 
Zn2SnO4:Cr3+, Zn2SnO4:Cr3+, Al3+ ..............................................................33 
2.2.1. Materials ................................................................................................. 33 
2.2.2. Synthesis of Zn2SiO4 .............................................................................. 33 
2.2.3. Synthesis of Zn2SiO4: Mn2+ ................................................................... 34 
2.2.4. Synthesis of Zn2SnO4 ............................................................................. 34 
2.2.5. Synthesis of Zn2SnO4:Mn2+ ................................................................... 34 
2.2.6. Synthesis of Zn2SnO4:Cr3+ and Zn2SnO4:Cr3+, Al3+ .............................. 34 
2.2.7. Mechanical milling ................................................................................. 35 
 iv 
2.3. Techincal methods .............................................................................35 
2.3.1. Structural characterisation ..................................................................... 35 
2.3.2. Photoluminescent characterization ........................................................ 30 
2.4. LED package process .........................................................................43 
2.4.1. Die bonding ........................................................................................... 44 
2.4.2. Wire Bonding ........................................................................................ 45 
2.4.3. Phosphor Dosing ................................................................................... 45 
2.4.4. Dispensing ............................................................................................. 46 
2.4.5. Curing .................................................................................................... 47 
2.4.6. Testing ................................................................................................... 47 
Chapter 3. STRUCTURE AND OPTICAL PROPERTIES OF Zn2SiO4 AND 
Zn2SiO4:Mn2+ PHOSPHORS ................................................................................ 48 
3.1. Introduction .......................................................................................48 
3.2. Structure and optical properties of Zn2SiO4 phosphors ........................49 
3.2.1. X-ray diffraction of Zn2SiO4 ................................................................. 49 
3.2.2. Phosphor morphology of Zn2SiO4 ........................................................ 50 
3.2.3. Vibrational analysis: Raman spectra of Zn2SiO4 .................................. 51 
3.3. Structure and optical properties of Zn2SiO4:Mn2+ phosphors ...............55 
3.3.1. X-ray diffraction of Zn2SiO4:Mn2+ ....................................................... 55 
3.3.2. Phosphor morphology of Zn2SiO4:Mn2+ ............................................... 57 
3.3.3. Vibrational analysis of Zn2SiO4:Mn2+ ................................................... 58 
3.3.4. Optical properties of Zn2SiO4:Mn2+ ...................................................... 61 
3.3.5. Thermoluminescence (TL) properties and Decay time of Mn2+ doped 
Zn2SiO4 ............................................................................................................. 64 
3.3.6. Application of Mn2+ doped Zn2SiO4 on UV LED................................. 66 
3.4. Conclusion .........................................................................................67 
Chapter 4. STRUCTURE AND OPTICAL PROPERTIES OF Zn2SnO4 AND 
Zn2SnO4:Mn2+ PHOSPHORS ............................................................................... 68 
4.1. Introduction .......................................................................................68 
4.2. Structural and optical properties of Zn2SnO4 phosphors ......................69 
4.2.1. X-ray diffraction of Zn2SnO4 ................................................................ 69 
4.2.2. Optical properties of Zn2SnO4 .............................................................. 74 
4.3. Structural and optical properties of Zn2SnO4:Mn2+ .............................80 
4.3.1. X-ray diffraction of Zn2SnO4:Mn2+ ....................................................... 80 
4.3.2. Phosphor morphology of Zn2SnO4:Mn2+ .............................................. 84 
4.3.3. Optical properties of Zn2SnO4:Mn2+ ..................................................... 84 
 v 
4.3.4. Decay time of 5%Mn2+ doped Zn2SnO4 ............................................... 89 
4.3.5. Temperature-dependent PL and internal quantum efficiency of 
Zn2SnO4:5%Mn2+ phosphors ........................................................................... 91 
4.3.6. Application of un-doped and Mn2+ doped Zn2SnO4 on LED ............... 92 
4.4. Conclusion .........................................................................................93 
Chapter 5. OPTICAL PROPERTIES OF Zn2SnO4:Cr3+ AND Zn2SnO4:Cr3+, Al3+ 
FOR PLANT CULTIVATION LED.................................................................... 95 
5.1. Introduction .......................................................................................95 
5.2. Structural and optical properties of Zn2SnO4:Cr3+ phosphors ..............97 
5.2.1. X-ray diffraction of Zn2SnO4:Cr3+ ........................................................ 97 
5.2.2. Phosphor morphology of Zn2SnO4:Cr3+ .............................................. 100 
5.2.3. Optical properties of Zn2SnO4:Cr3+ ..................................................... 101 
5.2.4. Application of the prepared phosphor for fabricating infrared LEDs . 105 
5.3. Structural and optical properties of Zn2SnO4:Cr3+, Al3+ phosphors 106 
5.3.1. X-ray diffraction and FESEM of Zn2SnO4:Cr3+,Al3+ .......................... 106 
5.3.2. Crystal field analysis ........................................................................... 109 
5.3.3. The effect of Al3+ on optical properties of ZTO: Cr3+ ........................ 111 
5.3.4. Application of the prepared phosphor ................................................. 116 
5.4. Conclusion ....................................................................................... 117 
CONCLUSIONS AND FUTURE WORKS ...................................................... 120 
PUBLICATIONS ............................................................................................... 123 
RELATED PUBLICATIONS ............................................................................ 124 
REFERENCES ................................................................................................... 125 
 vi 
LIST OF ACRONYMS 
Acronyms Full name 
EDX/EDS: Energy-Dispersive X-ray spectroscopy 
LED: Light Emitting Diode 
NIR: Near-infrared 
PL: Photoluminescence 
SEM: Scanning Electron Microscope 
XRD: X-Ray Diffraction 
FESEM: Field emission scanning electron Microscope 
PLE: Photoluminescence excitation 
UV: Ultraviolet 
HWHM: Half-Width at half-maximum 
IR: Infra-red 
TM: Transition Metal 
EL: Electroluminescence 
NBOH: Non – bridging oxygen hole centers 
RGB: Red, Green and Blue 
FTIR: Fourier – transform infrared spectroscopy 
HEBM: High – energy planetary ball mill 
AIST: Advanced Institute for Science and Technology 
JCPDS: Joint committee on powder diffraction standards 
FWHM: Full width at half maximum 
 vii 
Zni: Zinc interstitials 
Sni: Tin interstitials 
Oi: Oxygen interstitials 
Vo: Oxygen vacancy 
WBG: Wide band gap 
ZTO: Zinc stannate 
VZn: Zinc vacancy 
VSn: Tin vacancy 
TG-DTA: Thermogravimetry/Different thermal analyzer 
CRI: Color rendering index 
CCT: Correlated color temperature 
BM: Brurstein – Moss 
WLED White light-emitting diode 
QE Quantum efficiency 
AO Atomic orbitals 
 viii 
LIST OF FIGURES 
No. Name Page 
Figure 1.1 
Shapes of d orbitals and ligand positions ○: Ligands for 
octahedral symmetry: Ligands for tetrahedral symmetry 
11 
Figure 1.2 
The separation of AO d of the transition metal ions in 
octagonal symmetry 
12 
Figure 1.3 
The separation of AO d of the central ion by the crystal 
field in different symmetry 
13 
Figure 1.4 
The separation of energy levels of some transition metal 
ions due to electrostatic interaction (a) and the energy 
level separation of Cr3+ ions when take into account the 
spin-orbit interaction L-S (with B = 918 cm-1) (b) 
14 
Figure 1.5 3d level splitting caused by the crystal field 15 
Figure 1.6 
Energy level diagram for the d2 configuration. (From 
Kamimura, H., Sugano, S., and Tanabe, Y., Ligand Field 
Theory and its Applications, Syokabo, Tokyo, 1969 (in 
Japanese) 
16 
Figure 1.7 
Energy level diagram for the d3 configuration. (From 
Kamimura, H., Sugano, S., and Tanabe, Y., Ligand Field 
Theory and its Applications, Syokabo, Tokyo, 1969 (in 
Japanese) 
17 
Figure 1.8 
Energy level diagram for the d5 configuration. (From 
Kamimura, H., Sugano, S., and Tanabe, Y., Ligand Field 
Theory and its Applications, Syokabo, Tokyo, 1969 (in 
Japanese) 
17 
Figure 1.9 
Tanabe–Sugano diagram for the Mn2+ in Zn2SiO4 crystal 
field 
19 
Figure 1.10 
Tanabe–Sugano diagram for the Cr3+ electron 
configuration in the octahedral crystal field. C/B = 4.7 
21 
Figure 1.11 
(a) The number of SiO4− units that are connected together 
by sharing the oxygen atoms and (b) Structure of the 
Willemite -Zn2SiO4 
23 
Figure 1.12 Structural models for the cubic spinel -Zn2SnO4 25 
Figure 1.13 
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