STRUCTURAL, THERMAL AND OPTICAL PROPERTIES OF PR3+,

ER3+/DY3+ IONS SINGLY AND DOUBLY DOPED BOROTELLURITE GLASS SYSTEM FOR PHOTONIC APPLICATIONS

BASHAR KHUDHAIR ABBAS

FK 2020 52

i

STRUCTURAL, THERMAL AND OPTICAL PROPERTIES OF PR3+,

ER3+/DY3+ IONS SINGLY AND DOUBLY DOPED BOROTELLURITE

GLASS SYSTEM FOR PHOTONIC APPLICATIONS

By

BASHAR KHUDHAIR ABBAS

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirement for the Degree of Doctor of Philosophy

July 2020

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COPYRIGHT

All material contained within the thesis, including without limitation text, logos, icons,

photographs, and all other artwork, is copyright material of Universiti Putra Malaysia

unless otherwise stated. Use may be made of any material contained within the thesis

for non-commercial purposes from the copyright holder. Commercial use of material

may only be made with the express, prior, written permission of Universiti Putra

Malaysia.

Copyright © Universiti Putra Malaysia

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DEDICATION

TO

The soul of my father

My mother

My brothers & sisters

My family

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment

of the requirement for the degree of Doctor of Philosophy

STRUCTURAL, THERMAL AND OPTICAL PROPERTIES OF PR3+,

ER3+/DY3+ IONS SINGLY AND DOUBLY DOPED BOROTELLURITE

GLASS SYSTEM FOR PHOTONIC APPLICATIONS

By

BASHAR KHUDHAIR ABBAS

July 2020

Chairman : Professor Mohd Adzir bin Mahdi, PhD

Faculty : Engineering

Trivalent rare-earth (RE3+) ion doped or codoped glasses have promising

technological applications in fiber optical telecommunication systems (1.5 μm

region), color display devices, multi-channel wavelength-division multiplexing

(WDM) transmission, white (W-LEDs) and solid-state lighting (SSL) emission. In this

study, the evaluation of new potential candidate glasses of Pr3+, Er3+/Dy3+ ions singly,

and co-doped with a composition of 50B2O3-10 TeO2-10 PbO-10 ZnO-10 Li2O-10

Na2O (borotellurite host glasses) for an optical communication system and SSL/W-

LEDs has been made. Structural, thermal, and optical properties are investigated of

the glass samples were prepared by the melt-quenching method in polished solid and

powder forms. Accordingly, from X-ray Diffraction (XRD) measurements, the

amorphous-like structure was observed for all the prepared glasses. The presence of

various functional groups of borotellurite matrix was confirmed by Attenuated Total

Reflectance-Fourier Transform Infrared (ATR-FTIR) and Raman spectra. Thermo-

Gravimetric Analysis (TGA) analysis presented low weight loss for all synthesized

glasses. From the Differential Scanning Calorimetry DSC profiles the glass transition

temperature (Tg), onset crystallization temperature (Tx), and crystallization

temperature (Tc) were identified and evaluated as well as the related thermal

parameters. Optical absorption characterization was employed for all samples in UV-

Vis.-NIR region. From absorption spectra of Er3+ and Dy3+ singly doped glasses, Judd-

Ofelt theory was employed to evaluate their (J-O) intensity parameters (Ωλ, λ=2, 4 and

6) were they are following the same trend Ω2>Ω4>Ω6. Also, the computed ‘χ’=Ω4/Ω6

(spectroscopic quality factor) values are higher than some of the reported glass system.

Furthermore, using Judd–Ofelt intensity parameters, the radiative AR (s-1), branching

ratio (βR), radiative decay lifetimes τR (μs) for deferent emissions level were computed.

Pertaining to the photoluminescence in the visible region, under excitation of 350 nm

and 378 nm band, the singly and Er3+/Dy3+ co-doped glasses shows deferent color

emission in CIE diagram located at the green, blue and yellow-white region, where

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these color properties emphasize the potential usage in display, LED and laser

applications. Further, under 808 nm excitation, emission peak centered at 1532 nm

with an FWHM value of around ~69 which is due to 4I13/2→4I15/2 transition can be

observed from all the singly Er3+ and Er3+/Dy3+- codoped glasses. But their NIR

fluorescence intensity reduces with the Dy3+ content addition, which indicates the

possible ET between Er3+ and Dy3+ ions, suggesting that Dy3+ ions can be used to

depopulate Er3+: 4I13/2 level. On the other hand, under 980 nm excitation, 1.0%Er3+

glass possesses the highest NIR emission intensity at 1.532 μm with an FWHM value

of 62 nm. NIR emission in 1.0/1.0 Er3+/Dy3+ has completely quenched by the presence

of Dy3+ ions, suggesting an efficient ET from Er3+→Dy3+. The singly doped glass (1.0

mol% Er3+) which exhibits the highest intensity at 1.532 μm NIR emission under 980

nm excitation has the highest cross-section value of (2.669 ×10-20 cm2), and an optical

gain bandwidth value of (1.65×10-25 cm3) suggested this glass as a potential candidate

for 1.532 μm optical fiber laser in telecommunication application systems. Also, the

singly and Pr3+/Dy3+ co-doped glasses are evaluated by means of optical properties

such as their optical band gap energy (𝐸𝑔𝑜𝑝𝑡

) in the UV-Visible region for direct and

indirect transitions found to be decreased as the Pr3+ ion concentration increases,

which means the increment of donor center content in the glass matrix. Further, the

energy level diagram confirmed the mutual energy transfer (Pr3+ Dy3+) under 437

nm and 388 nm excitations. Lastly, the CIE chromaticity results confirm that white

warm/neutral as well as reddish-orange light color can be attained by tuning the

excitation wavelength. Finally, upon the above findings, the aforementioned glasses

(Er3+, Pr3+/Dy3+ singly and doubly doped) are suggested as a useful candidate for the

optical communication system in addition to the W-LEDs and SSL applications.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai

memenuhi keperluan untuk ijazah Doktor Falsafah

STRUKTUR, SIFAT TERMA DAN OPTIK SISTEM KACA

BOROTELLURIT TERDOP TUNGGAL DAN BERSAMA ION-ION PR3+,

ER3+/DY3+ UNTUK KEGUNAAN FOTONIK

Oleh

BASHAR KHUDHAIR ABBAS

Julai 2020

Pengerusi : Profesor Mohd Adzir bin Mahdi, PhD

Fakulti : Kejuruteraan

Kaca-kaca terdop atau terdop-bersama ion tri-valens nadir bumi mempunyai kegunaan

teknologi yang berpotensi di dalam sistem telekomunikasi gentian optik (julat 1.5 μm),

peranti-peranti paparan berwarna, transmisi multi-saluran multipleksi panjang

gelombang-terbahagi (WDM), pancaran putih (W-LEDs) dan pencahayaan keadaan

pepejal (SSL). Di dalam kajian ini, penilaian ke atas potensi baharu kaca-kaca terpilih

terdop tunggal dan terdop-bersama ion-ion Pr3+, Er3+/Dy3+ dengan komposisi 50B2O3-

10 TeO2-10 PbO-10 ZnO-10 Li2O-10 Na2O (kaca hos borotellurit) untuk kegunaan

sistem komunikasi optik dan SSL/W-LEDs telah dilakukan.

Struktur, sifat terma dan optik sampel-sampel kaca telah dikaji dan dihasilkan melalui

kaedah sepuh lindap di dalam keadaan pepejal dan serbuk. Berdasarkan pengukuran

belauan sinar-X (XRD), struktur amorfus telah diperhatikan untuk kesemua kaca-kaca

dihasilkan. Kehadiran pelbagai kumpulan-kumpulan fungsian matrik borotellurit

dipastikan melalui spektra Inframerah Terubah Fourier-Pantulan Penuh (ATR-FTIR)

dan Raman. Analisis Termo-Gravimetrik menunjukkan kehilangan berat rendah untuk

kesemua kaca-kaca yang disintesis. Hasil dari profil Kalorimetri Imbasan Pembeza,

DSC suhu peralihan kaca (Tg), suhu awalan pembentukan kristal (Tx) dan suhu

pembentukan kristal (Tc) telah diperolehi dan penilaian parameter-parameter berkaitan

sifat terma telah dilakukan. Pencirian penyerapan optik telah dilakukan ke atas semua

sampel di dalam julat UV-Vis.-NIR. Berdasarkan dari spektra kaca-kaca terdop

tunggal Er3+ dan Dy3+, teori Judd-Ofelt telah digunakan untuk perhitungan parameter-

parameter keamatan (J-O) (Ωλ, λ=2, 4 dan 6) dan dapatan kecenderungan adalah

Ω2>Ω4>Ω6. Didapati juga nilai-nilai hitungan ‘χ’=Ω4/Ω6 (faktor kualiti spektroskopik)

adalah tinggi berbanding antara sistem kaca yang dilaporkan. Seterusnya, melalui

parameter-parameter keamatan Judd-Ofelt, pancaran nisbah cabangan (βR), susutan

masa hayat pancaran τR (μs) untuk pancaran aras berbeza telah dihitung. Berkaitan

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fotoluminesens di dalam julat nampak, dengan pengujaan jalur 350 nm dan 378 nm

kaca-kaca terdop tunggal dan terdop-bersama Er3+/Dy3+ menunjukkan pancaran

warnaan berbeza di dalam rajah CIE pada julat kedudukan hijau, biru dan kuning-

putih, di mana sifat-sifat warna ini memperjelaskan potensi aplikasi paparan, LED dan

laser. Tambahan pula dengan pengujaan 808 nm, pancaran puncak berpusat pada 1532

nm dengan nilai FWHM sekitar ~69 nm disebabkan peralihan 4I13/2→4I15/2 dapat

diperhatikan daripada kesemua kaca-kaca terdop tunggal Er3+ dan terdop-bersama

Er3+/Dy3+. Sebaliknya keamatan fluoresens NIR kaca-kaca ini menyusut dengan

peningkatan kandungan Dy3+, yang menjelaskan kemungkinan ET di antara ion-ion

Er3+ dan Dy3+, seterusnya mencadangkan ion Dy3+ dapat digunakan untuk

menyahpopulasikan aras Er3+: 4I13/2. Dalam pada itu, dengan pengujaan 980 nm, kaca

1.0% Er3+ mempunyai keamatan tertinggi pancaran NIR pada 1.532 μm dengan nilai

62 nm FWHM. Pancaran NIR untuk kaca 1.0/1.0 Er3+/Dy3+ telah menyusut

sepenuhnya dengan kehadiran ion Dy3+, mencadangkan ET yang efisen daripada

Er3+→Dy3+. Kaca terdop tunggal (1.0 mol% Er3+) yang menghasilkan keamatan

tertinggi pancaran NIR pada 1.532 nm dengan pengujaan 980 nm mempunyai nilai

keratan-rentas tertinggi (2.669 ×10-20 cm2), dan nilai lebar-jalur gandaan optik

(1.65×10-25 cm3) mencadangkan kaca ini sebagai calon berpotensi laser gentian optik

di dalam aplikasi sistem telekomunikasi. Tambahan lagi, penilaian sifat-sifat optik

kaca-kaca terdop tunggal Er3+ dan terdop-bersama Er3+/Dy3+ berkaitan tenaga jurang

jalur optik (𝐸𝑔𝑜𝑝𝑡

) dalam julat UV-Nampak untuk peralihan terus dan tidak-terus

didapati berkurangan dengan pertambahan kandungan ion Pr3+, menjelaskan

pertambahan kandungan pusat pengeluar di dalam matrik kaca. Seterusnya rajah aras

tenaga memperakui peralihan tenaga mutual (Pr3+ Dy3+) dengan pengujaan 437 nm

dan 388 nm. Akhirnya, keputusan kromatisiti CIE memperakui warnaan putih

suam/neutral dan juga oren kemerahan boleh diperolehi melalui pelarasan gelombang

pengujaan. Kesimpulannya kesemua penemuan-penemuan terhadap kaca-kaca

dinyatakan di atas (kaca-kaca terdop tunggal Er3+ and terdop-bersama Er3+/Dy3+)

mencadangkan calon yang berpotensi untuk sistem komunikasi optik di samping

aplikasi W-LEDs and SSL.

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ACKNOWLEDGEMENTS

First of all, I would like to express my gratitude to my supervisor, Prof. Dr. Mohd

Adzir bin Mahdi for his continuous support, invaluable guidance, and patience as

well as his encouragement and inspiration along this research journey without which

this thesis could not be done as smoothly as it did. I am very thankful for all the tasks

he produced for me. God bless him and his family.

Deep gratitude also goes to my co-supervisor Dr. Sharudin Bin Omar Baki for this

helpful guide on the research and thesis draft. He helped to improve the quality of this

work. God bless him and his family.

Also, I would like to express my sincere gratitude to my supervisory committee

members,

Dr. Mohd Hafiz bin Mohd Zaid for his constructive suggestions during my research

period and for supporting me through my studying time

To my dear friends and peers, I am so grateful to have companions like you by my

side during this journey to pursue my degree. It is you who made me feel warm all the

time, making my life abroad complete and colorful.

Most importantly, I want to say thanks to my wife and my brothers and sisters. They

helped me out during the difficult times in life and provided me with warm

encouragement.

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfilment of the requirement for the degree of Doctor of Philosophy. The

members of the Supervisory Committee were as follows:

Mohd Adzir bin Mahdi, PhD

Professor

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Sharudin bin Omar Baki, PhD

Senior Lecturer

Centre of Foundation Studies for Agricultural ScienceUniversiti Putra Malaysia

(Member)

Mohd Hafiz bin Mohd Zaid, PhD

Senior Lecturer

Faculty of Science

Universiti Putra Malaysia

(Member)

ZALILAH MOHD SHARIFF, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date: 12 November 2020

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Declaration by graduate student

I hereby confirm that:

this thesis is my original work;

quotations, illustrations and citations have been duly referenced;

this thesis has not been submitted previously or concurrently for any other degree

at any institutions;

intellectual property from the thesis and copyright of thesis are fully-owned by

Universiti Putra Malaysia, as according to the Universiti Putra Malaysia

(Research) Rules 2012;

written permission must be obtained from supervisor and the office of Deputy

Vice-Chancellor (Research and innovation) before thesis is published (in the form

of written, printed or in electronic form) including books, journals, modules,

proceedings, popular writings, seminar papers, manuscripts, posters, reports,

lecture notes, learning modules or any other materials as stated in the Universiti

Putra Malaysia (Research) Rules 2012;

there is no plagiarism or data falsification/fabrication in the thesis, and scholarly

integrity is upheld as according to the Universiti Putra Malaysia (Graduate

Studies) Rules 2003 (Revision 2012-2013) and the Universiti Putra Malaysia

(Research) Rules 2012. The thesis has undergone plagiarism detection software

Signature: Date:

Name and Matric No: Bashar Khudhair Abbas, GS51747

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Declaration by Members of Supervisory Committee

This is to confirm that:

the research conducted and the writing of this thesis was under our supervision;

supervision responsibilities as stated in the Universiti Putra Malaysia (Graduate

Studies) Rules 2003 (Revision 2012-2013) were adhered to.

Signature:

Name of Chairman

of Supervisory

Committee:

Professor Dr. Mohd Adzir bin Mahdi

Signature:

Name of Member

of Supervisory

Committee:

Dr. Sharudin bin Omar Baki

Signature:

Name of Member

of Supervisory

Committee:

Dr. Mohd Hafiz bin Mohd Zaid

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TABLE OF CONTENTS

Page

ABSTRACT i

ABSTRAK iii

ACKNOWLEDGEMENTS v

APPROVAL vi

DECLARATION viii

LIST OF TABLES xiii

LIST OF FIGURES xv

LIST OF ABBREVIATIONS xix

CHAPTER

1 INTRODUCTION 1 1.1 Introduction to Glass 1 1.2 Rare-Earth Ions (RE+) 1 1.3 Problem Statement 2 1.4 Aim and Objectives 3 1.5 Thesis Outlines 3

2 LITERATURE REVIEW 5

2.1 Fundamentals of Glass Structure 5 2.1.1 Glass Definition 5 2.1.2 Glass Enthalpy Transformation Phases 5 2.1.3 Crystalline Solid and Amorphous Glass 6

2.2 Glass Formation Theories 7 2.2.1 Structural Approaches of Glass Formation 7

2.2.1.1 Goldschmidt’s Theory 8 2.2.1.2 Zachariasen’s Theory 8 2.2.1.3 Energetic Based Model 9

2.2.2 Kinetic Approaches of Glass Formation 11

2.3 Glass Formation Based Chemicals 13 2.3.1 Borate Glass 14

2.3.2 Tellurite Glass 16 2.3.3 Borotellurite as Host Glass 17

2.4 Solid-State Lighting (SSL) and White-Light Emitting Diode

(W-LED)

17

2.5 Rare Earth Doped Glasses 19

2.5.1 Rare Earth Ions Properties 20

3 RARE EARTH THEORY 22 3.1 Energy Levels Scheme 22 3.2 Radiative and Non-Radiative Transitions 24

3.3 Ion-Ion Interaction 28 3.3.1 Cross Relaxation (CR) 28

3.3.2 Up-Conversion Energy Transfer 29

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3.3.3 Fluorescence Quenching 30 3.4 Decay Lifetime Limitation Parameters 31

3.4.1 Spontaneous Emission 32 3.4.2 Self-Absorption 33 3.4.3 Phonon Decay 33

3.5 Judd-Offelt Theory 34 3.6 CIE Chromaticity and Correlated Color Temperature 37

4 METHODOLOGY 38 4.1 Glass Fabrication 38

4.1.1 Glass Composition and Batching 38 4.1.2 Glass Formation 42

4.2 Structural Characterization 44

4.2.1 XRD (X-ray Diffraction) 44 4.2.2 ATR-FTIR Spectroscopy 45 4.2.3 Raman Spectroscopy 45

4.3 Thermal Characterization (TGA/DSC) 46 4.4 Optical Characterization 48

4.4.1 Optical Absorption 48 4.4.2 Visible Luminescence and Decay Lifetime 49 4.4.3 NIR Luminescence and Decay Lifetime 50

5 RESULTS AND DISCUSSION 51 5.1 Host and Er3+/Dy3+ Ions Singly and Doubly Doped

Borotellurite Glass

51

5.1.1 Structural Analysis 51 5.1.1.1 X-ray Diffraction (XRD) and EDAX

Analysis

51

5.1.1.2 Fourier-Transform Infrared (FT-IR)

Analysis

54

5.1.1.3 Raman Spectroscopy Analysis 55 5.1.2 Thermal Studies 59

5.1.2.1 Thermogravimetric Analysis (TGA) 59 5.1.2.2 Differential Scanning Calorimetry (DSC)

Analysis

61

5.1.3 Optical Analysis 63

5.1.3.1 Optical Absorption and Judd-Ofelt (J-O)

Analysis

63

5.1.3.2 Photoluminescence, Decay Lifetime and

Chromaticity Analysis 78

5.1.3.3 Near-Infrared (NIR) Luminescence and

Decay Lifetime Analysis

94

5.2 Pr3+, Dy3+ Ions Singly and Doubly Doped Borotellurite

Glass

102

5.2.1 Structural Analysis 103 5.2.1.1 X-ray Diffraction (XRD) and EDAX

Analysis

103

5.2.1.2 Fourier Transform Infrared (FT-IR)

Analysis 104

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5.2.1.3 Raman Spectroscopy Analysis 106 5.2.2 Thermal Analysis (TGA/DSC) 108 5.2.3 Optical Analysis 110

5.2.3.1 Absorption, Excitation and Tauc’s

Spectra Analysis

110

5.2.3.2 PLE/PL and Decay Lifetime Analysis 115 5.2.3.3 Chromaticity (CIE) Analysis 122

5.3 Chapter Summary 124

6 CONCLUSIONS AND FUTURE WORKS 127 6.1 Conclusion 127 6.2 Contribution 128

6.3 Future Works 129

REFERENCES 130 APPENDICES 146 BIODATA OF STUDENT 150 LIST OF PUBLICATIONS 151

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LIST OF TABLES

Table Page

2.1 Classification of cations as network formers, network modifiers, and

intermediates [1]

9

2.2 Pauling electronegativities of glass formers and network modifiers

[58] 10

2.3 Bond strengths for selected oxides [61] 12

4.1 Glass samples composition in mol% of the first part of this study 39

4.2 Glass samples composition in mol% of the second part of this study 39

4.3 Glass components and chemicals used to batch glasses, molecular

weight (MW), purity and sources

40

4.4 Batch calculation (15 g) for host glass 41

5.1 FTIR band assignment for the prepared glasses 55

5.2 Identified Raman bands 58

5.3 Identified DSC temperatures of the synthesized glasses 63

5.4 Absorption band assignments (from the ground state, 4I15/2), energy,

experimental (fexp) and calculated (fcal) oscillator strengths and

corresponding residuals of (ⅰ) 0.5 mol% Er3+ (Glass “B”) and (ⅱ)

1.0 mol% Er3+ (Glass “C”)-doped glasses along with J‒O parameters

68

5.5 Absorption band assignments (from the ground state, 6H15/2), energy,

experimental (fexp) and calculated (fcal) oscillator strengths and

corresponding residuals of (ⅰ) 0.5 mol% Dy3+ (Glass “D”) and

(ⅱ) 1.0 mol% Dy3+ (Glass “E”)-doped glasses along with J‒O

parameters

69

5.6 Comparison of Judd–Ofelt intensity parameters (Ωλ), their trend and

spectroscopic quality factor (χ) of Er3+-doped various glass systems 70

5.7 Comparison of Judd–Ofelt intensity parameters (Ωλ), their trend and

spectroscopic quality factor (χ) of Dy3+-doped various glass systems 71

5.8 Emission transitions (SLJ SLJ), wavelength, electric (Aed) and

magnetic (Amd) dipole transition probabilities, total predicted radiative

transition probabilities (AR,), branching ratios (βR) and radiative decay

times (R) of luminescent levels in 0.5 mol% Er3+-doped glass

72

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5.9 Emission transitions (SLJ SLJ), wavelength, electric (Aed) and

magnetic (Amd) dipole transition probabilities, total predicted radiative

transition probabilities (AR), branching ratios (βR) and radiative decay

times (R) of luminescent levels in 1.0 mol% Er3+-doped glass

74

5.10 Emission transitions (SLJ SLJ), wavelength, electric (Aed) and

magnetic (Amd) dipole transition probabilities, total predicted radiative

transition probabilities (AR), branching ratios (βR) and radiative decay

times (R) of luminescent levels in 0.5 mol% Dy3+-doped glass

76

5.11 Emission transitions (SLJ SLJ), wavelength, electric (Aed) and

magnetic (Amd) dipole transition probabilities, total predicted radiative

transition probabilities (AR), branching ratios (βR) and radiative decay

times (R) of luminescent levels in 1.0 mol% Dy3+-doped glass

77

5.12 Emission peak wavelength (λp), full-width at half maximum (FWHM,

Δλp), measured lifetime (τm), stimulated emission cross-section (𝝈𝑷𝑬

), gain bandwidth (FWHM×(𝝈𝑷𝑬 )), and gain per unit length (τm

×(𝝈𝑷𝑬 )) of (ⅰ) green (4S3/24I15/2) emission in singly 0.5, and 1.0

mol% Er3+- doped glasses and (ⅱ) yellow (4F9/26H13/2) emission in

singly 0.5 and 1.0 mol% Dy3+-doped glasses

86

5.13 CIE Color coordinates (x, y) derived from the visible emission spectra

(Fig. 5.7 (b), Fig. 5.8 (b), Fig. 5.10 (a)) of all the “B‒I” glasses 94

5.14 FTIR band assignment for the prepared glasses 104

5.15 Observed Raman bands from Fig. 5.19 and their assignment 108

5.16 Thermal properties of the glasses 110

5.17 Direct and indirect optical band gaps of studied glasses 115

5.18 CIE Chromaticity Parameters (Fig. 5.27 (a)) 124

5.19 CIE Chromaticity Parameters (Fig. 5.27 (b)) 124

5.20 Major optical properties of the prepared glasses 126

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LIST OF FIGURES

Figure Page

2.1 Glass transformation phases [53] 6

2.2 Lattice structure of (a) amorphous (b) crystalline solid [1] 7

2.3 General time-temperature-transformation (TTT) curve for glass

forming melt [64] 13

2.4 Structural groups present in alkali borate glasses as proposed by

Krogh- Moe: a) boroxol, b) pentaborate, c) triborate and d) diborate

groups [75]

14

2.5 Schematic picture of the TeO2 unit in the structure of α-TeO2 [79] 16

2.6 Luminous efficiency [83] 18

2.7 Projected cost of light [85] 19

2.8 Rare Earth position in periodic table 20

3.1 Rare-earth ions of focus in this thesis 22

3.2 a) Energy level of trivalent RE [102], b) Energy levels of free RE ion

and host matrix field [122]

23

3.3 Transition mechanisms between two energy levels (a) absorption, (b)

spontaneous emission, and (c) stimulated emission [104]

25

3.4 Transition rates between two energy levels at equilibrium condition:

(a) Absorption, (b) Spontaneous emission rates and (c) Stimulated

emission [105]

26

3.5 Non-radiative relaxation rate as a function of the energy gap for the

indicated glasses [109] 27

3.6 a) Cross relaxation of Tm3+ between the 3H4 and 3H6 manifold [110],

b) Energy transfer up-conversion (ETU) following energy transfer

(ET) [111]

29

3.7 Determination of lifetime using a pulsed laser and time resolved

measurements. (a) A narrow excitation pulse and (b) The time decay

of the resulting fluorescence [121]

32

4.1 Schematic diagram of desk-top high temperature muffle furnace 42

4.2 a)Glass samples fabrication steps, b) Sample photos (Table 4.1) and c)

Sample photos (Table 4.2)

43

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4.3 Schematic diagram of diffractometer system 44

4.4 Schematic diagram of FTIR spectrometer 45

4.5 Schematic diagram of Raman spectrometer 46

4.6 Schematic diagram of thermal gravimetric analyzer (a) DSC. (b) TGA 47

4.7 Schematic diagram of UV–Vis–NIR Spectrophotometer 49

4.8 Schematic diagram of spectrofluorometric 50

4.9 Schematic diagram of spectrometer (NIR-Emission) 50

5.1 a) XRD-profiles of glasses (A-I). b, c) EDAX profile of host glass (A)

and codoped glass (H), respectively

53

5.2 FTIR spectra for (A-I) prepared glasses within the 290-1600 cm-1

wavenumber region

54

5.3 (a-i) Raman spectra for all the prepared (A-I) glasses within the 50-

1600 cm-1 wavenumber region. 57

5.4 (a) Thermo-gravimetric analysis (TGA) (inset, from 700 to 1000 °C).

(b-j) Differential scanning calorimetry (DSC) profiles for (A-I)

synthesized glasses. In Figure 5.4 (a) inset plot, the line drawn at 800

°C as guide to the eyes indicates the starting point of the weight loss

for 800 ‒1000 °C temperature range

61

5.5 Cut-off wavelength of the host glass (A) in UV-Vis range 63

5.6 Optical absorption spectra of the (a) 0.5 mol% Er3+ (inset, 1.0 mol%

Er3+), (b) 0.5 mol% Dy3+, (c) 1.0 mol% Dy3+ singly doped glasses and

(d) (0.5; 1.0 mol%) Er3+/(0.5, 1.0 mol%) Dy3+ codoped glasses

66

5.7 (a) Photoluminescence excitation (PLE) spectra for the singly 0.5, 1.0

mol% Er3+- doped glasses by monitoring emission at 554 nm; (b)

Photoluminescence (PL) spectra for singly 0.5, 1.0 mol% Er3+-doped

glasses under 378 nm excitation wavelength

79

5.8 (a) Photoluminescence excitation (PLE) spectra for the singly 0.5,

1.0 mol% Dy3+-doped glasses by monitoring emission at 574 nm and

(b) Photoluminescence (PL) spectra for singly 0.5, 1.0 mol% Dy3+-

doped glasses under 350 nm excitation wavelength

81

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5.9 Decay lifetime profiles for the 4S3/2 level of (a) 0.5 mol % Er3+ and (b)

1.0 mol % Er3+-doped glasses under 378 nm excitation wavelength

with single exponential fit results. (c) decay lifetime profiles for the 4F9/2 level of 0.5 and 1.0 mol % Dy3+-doped glasses under 350 nm

excitation wavelength. Inokuti-Hirayama (I‒H) model fit for (d) 0.5

mol % Dy3+ and (e) 1.0 mol % Dy3+-doped glasses. (f) Partial energy-

level diagrams of the Er3+ and Dy3+ ions for the singly-doped glasses

depicting PLE, PL, along with the non-radiative (NR), RET and cross-

relaxation (CR) channels

85

5.10 (a) Photoluminescence (PL) spectra for (0.5; 1.0 mol%) Er3+/ (0.5,

1.0 mol%) Dy3+-codoped glasses under 378 nm excitation wavelength.

(b) Photoluminescence (PL) spectra for singly 0.5, 1.0 mol% Dy3+-

doped glasses under 378 nm excitation wavelength.

Photoluminescence excitation (PLE) spectra for (0.5 mol% Er3+/0.5,

1.0 mol% Dy3+)-codoped glasses by monitoring emissions at (c) 540

nm and (d) 584 nm. Photoluminescence (PL) spectra for (0.5 mol%

Er3+/0.5, 1.0 mol% Dy3+)-codoped glasses under (e) 518 nm and (f) 396

nm excitation wavelengths. Decay lifetime profiles of 0.5 Er3+, 0.5

Dy3+ (mol%)-singly doped and 0.5 Er3+/0.5 Dy3+ (mol %)-codoped

glasses under (g) 518 nm (λem. = 540 nm) and (h) 396 nm (λem. = 482

nm) excitation wavelengths

91

5.11 CIE chromaticity diagram for all the studied Er3+ (glasses B, C), Dy3+

(D, E glasses)- singly doped and Er3+/Dy3+ (glasses F, G, H, I)-codoped

glasses under 378 and 350 nm excitation wavelengths

93

5.12 NIR emission spectra for the studied glasses under (a) 808 nm and (b)

980 nm LD excitations 95

5.13 NIR emission (4I13/24I15/2) decay profiles with single exponential fit

results for (a) 0.5 Er3+ (b) 1.0 Er3+-singly doped, and (c) 0.5 Er3+/0.5

Dy3+, (d) 0.5 Er3+/1.0 Dy3+ and (e) 1.0 Er3+/0.5 Dy3+-codoped glasses

under 980 nm LD excitation

97

5.14 Energy-level scheme and possible energy transfer (ET) processes from

Er3+ to Dy3+ ion in the studied Er3+/Dy3+-codoped glasses under (a) 808

nm and (b) 980 nm LD excitations

99

5.15 Stimulated emission cross-section profile of the 4I13/24I15/2 transition

for the 1.0 mol% Er3+- singly doped glass under 980 nm LD

excitation

101

5.16 Predicted theoretical gain spectra of the 4I13/24I15/2 emission transition

for the singly 1.0 mol% Er3+-doped glass

102

5.17 a) XRD patterns of the studied glass samples (S2-S7). b) EDAX profile

of codoped glass (S7)

103

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5.18 FTIR spectra of glass samples within the spectral range of (a) 200-1600

cm-1 and b) 1500-4000 cm-1

105

5.19 Raman spectra for all the studied glasses 106

5.20 a) TGA of all glass samples (S2-S7) and b) DCS profiles of (S2-S7)

glass samples 109

5.21 Optical absorption spectra of a) S2 (0.5 mol% Pr6O11) glass and b) S3-

S7 glasses

111

5.22 Tauc’s plot for allowed direct transitions (n=2) of (a) S1(0.5 mol %

Dy2O3) and S2 (0.5 mol% Pr6O11) singly doped glasses and (b) S3-S7

co-doped glasses. Tauc’s plot for allowed indirect transitions (n=1/2)

of (c) S1(0.5mol % Dy2O3) and S2 (0.5 mol % Pr6O11) singly doped

glasses and (d) S3-S7 co-doped glasses

114

5.23 a) Excitation and emission spectra of S1 (Dy3+) singly doped glass

(λemi=574 nm and λexc=388 nm), b) Emission spectra of S1 and S3-S7

glasses under λexc=388 nm, c) Excitation and emission spectra of S2

(Pr3+) singly doped glass (λemi=624 nm and λexc=433 nm), and d)

Emission spectra of S2-S7 glasses under λexc=443 nm

117

5.24 Dy3+ (574 nm) emission decay profiles of samples (S3-S7) under 388

nm excitation. Solid lines are fits to Eq. (5.5) for dipole-dipole (dd),

dipole-quadrupole (dq) and quadrupole-quadrupole (qq) interactions

119

5.25 Decay curves of 574 nm emission for the S1 and S3-S7 samples under

388 nm excitation. Lifetimes (𝝉𝑫𝒚) and energy transfer efficiencies (𝜼)

are listed in inset table

120

5.26 Energy transfer processes between Pr3+ and Dy3+ ions under λexc = 388

nm (ET1) and λexc = 443 nm (ET2)

121

5.27 CIE1931 chromaticity luminescence diagram colors for the glasses

(S1-S7) under excitation wavelengths a) 388 nm and b) 443 nm)

123

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LIST OF ABBREVIATIONS

ATR-FTIR Attenuated Total Reflectance-Fourier Transform Infrared

BP Boson Peak

CR Cross Relaxation

DSC Differential Scanning Calorimetry

DWDM Dense Wavelength Division Multiplexing

Dy3+ Dysprosium ions

ED Electric Dipoles

ED Electrical Dipole

EDAX Energy Dispersive X-ray Analysis

EDFA Erbium-Doped Fiber Amplifier

Er3+ Erbium ions

ESA Excited State Absorption

ET Energy Transfer

ETU Energy Transfer Up-conversion

FWHM Full-Width at Half-Maximum

GSA Ground State Absorption

HMO Heavy Metal Oxide

J Total Angular Momentum

J-O Judd-Ofelt

LD Laser Diode

MD Magnetic Dipoles

MIR Mid Infrared

MPR Multi Phonon Relaxation

MW Molecular Weight

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NBO Non-Bridging Oxygen

NIR Near-Infrared

PL Photo Luminescence

PLE Photo Luminescence Excitation

Pr3+ Praseodymium ions

RE3+ Rare Earth ions

REEs Rare Earth Elements

RET Resonance Energy transfer

Scalc. Theoretical Electric Dipole Line Strength

Sed. Electric Dipole Line Strength

SEM Scanning Electron Microscopy

Sm3+ Samarium ions

Smeas. Measured Line Strength

SSL Sold-State Laser

Tc Peak Crystallization Temperature

TDA Differential Thermal Analysis

Tg Transition Temperature

TGA Thermo-Gravimetric Analysis

Tm Melting Temperature

TM Transition Metal

TPA Two-photon absorption

TTT Time-Temperature-Transformation

Tx Onset Crystallization Temperature

UC Up Conversion

UCL Up Conversion luminescence

UV Ultra Violet

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VIS Visible

WDM Wavelength Division Multiplexing

Wnr Nonradiative Rate

XRD X-ray Diffraction

α(λ) Optical Absorption Coefficient

η Quantum Efficiency

τexp. Measured Lifetimes

Ωλ JO Intensity Parameters

𝜏𝑅 Radiative Decay Lifetimes

∆ Glass Stability Factor

∆E Energy Gap

Ø Bridging Oxygen

p Phonon Energy

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CHAPTER 1

1 INTRODUCTION

1.1 Introduction to Glass

The glass existence in our living environment is so important as it is employed for

numerous applications. The traditional melt-quenching method of raw material is the

main method employed by humans to produce glasses. Due to the advent of the

technology many new applications are utilizing the glasses. Deferent modern devices

became valuable with the attendance of glasses such as vacuum tubes, monitors and

cell phones. The development of glass in near-infrared region applications like optical

fibers has revolutionized the telecommunications transmission data were expanding

the bandwidth of the transmission channels throughout the world [1]. Upon the

composition and the method of the glass formation, the obtained structure could be in

an amorphous or crystal state. The numerous kind of glass, such as Oxide-based

glasses (borates, silicates, germinates, or phosphates) are depending on which of the

glass-forming oxides (SiO2, B2O3, P2O5, or GeO2) used to make up their matrix

structure [2]. Much consideration is given lately for optical glasses due to their

transparency as well as the doping ability with the rare earth elements. The amorphous

phase of glass has been commonly used as a host matrix for RE ions doping due to

their properties over crystalline solid-state materials like wide transparency, various

glass compositions can be prepared, recycling capability, less formation time, easy to

be indifferent shapes (rod, disc), the ability to dope a large number of RE ions and the

possibility of constructing larger laser gain media with good optical quality [3-6].

1.2 Rare-Earth Ions (RE+)

A group of seventeen chemical elements represents the rare earth element where they

are located at the bottom of the periodic table. The group starts with yttrium and the

fifteen lanthanide elements were ended by lutetium. The International Union of Pure

and Applied Chemistry includes scandium in their rare earth element definition. The

RE+-doped glasses properties promote them to be interesting materials for the

mentioned applications such as fluorescence over UV-Vis-IR spectral regions, longer

lifetimes and higher quantum efficiency [15]. The optical features, as well as the

quantum efficiency parameters, are considered the most important parameter for rare

earth ions doping due to their significant contribution to the improvement of

optoelectronic devices like computer memory, catalytic converters DVDs, fluorescent

lighting, rechargeable batteries, cell phones, magnets, and much more [7-8]. It well

knows that the fluorescence properties of RE3+ ions depend on the host environment.

Thus, numerous research has been carried out to expand new glass materials

containing RE3+ ions with high quantum efficiency. Doping optical glasses with

trivalent rare-earth (RE) ions and their merits lead researchers to focus on them,

according to their widespread applications in display devices, optical fiber amplifiers,

high-intensity optical devices, optical information processing, optoelectronic devices,

non-invasive temperature sensors, lasers, solar cells, and solid-state lighting (SSL)

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technology [9-15]. The solid-state lighting SSL poses many promising properties and

principal advantages such as low power consumption, a wide range of spectral

wavelength emission, long-life, and low-cost. [16]. The demand for huge data

transmission is increasing. So, the researchers investigate more material and elements

were they could be employed for optical communication networks. Many applications

like wavelength division multiplexing (WDM) and dense wavelength division

multiplexing (DWDM) with wide and flat gain spectrum became an important key in

optical telecommunication [17-18]. The RE-doped glasses may be considered as

distinguished luminescence materials for their applications in SSL and fiber laser

amplifiers following their visible and NIR emissions in addition to their facile

manufacturing processes and good thermal stability. [19-23].

1.3 Problem Statement

The development of many optical and optoelectronic devices such as optical fiber

applications and solid-state lighting (SSL) prevailingly depends on Rare-earth (RE+)-

doped glasses due to their intense emissions by 𝑓4 − 𝑓4 and 𝑓4 − 𝑑 5 levels [24-26].

Thus, there is always a need for promising host material to be doped with RE+ ion for

developing a fiber laser amplifier in telecommunication window applications as well

as an economic, pollution-free and highly efficient SSL/W-LED device [36-41].

However, for borate glasses, the higher phonon energy (~1300–1500 cm−1) is a main

limiting factor for the required photonic applications when doped with RE ions

because it causes reducing the fluorescence and quantum efficiencies. It is well known

that TeO2 element has low phonon energy (~700–800 cm−1), wide optical transparency

up to ~6 μm, larger refractive index, higher chemical and thermal stability [42].

Therefore, it is hypothesised that borotellurite as a host glass demonstrates a

combination of attractive physical, chemical, mechanical and optical properties for

both borate and tellurite networks where they can be employed for visible and near

infrared applications [43]. Trivalent rare-earth (RE3+) ions doped or codoped with

host glass have promising technological applications such as in near-mid-infrared

(NIR-MIR) lasers within 1.2‒5 μm wavelength region in existing telecommunication

systems [35]. Regarding the optical fiber amplifier in telecommunication systems, Er3+

ion exhibits fluorescence at ~1.5 μm due to the efficient transition of 4I13/2→ 4I15/2 and 4I11/2 → 4I13/2 levels [47]. Also, Er3+ ion exhibit several intense emissions at blue,

green, and red wavelengths were they are useful for SSL applications. Moreover, due

to the ladder-like energy level structure of Er3+ and dysprosium Dy3+, both ions are

employed in this study by means of singly and doubly doped investigation as well as

the analysis of mutual energy transfer between them. On the other hand, white light-

emitting diodes (W-LEDs) being an interesting field for researchers. The (W-LEDs)

has been a favorite source for the replacement of traditional sources like fluorescent

lamps and incandescent bulbs due to the interesting significant properties such as long

lifetime, low power consumption, compactness, efficient energy, good reliability,

safety, high brightness, friendly environmental and excellent performance with low-

temperature [27-29]. Thereby, the highly efficient luminescence RE+-doped glass is

favorable for W-LEDs fabrication due to their thermal stability, high transparency,

low cost, and free halo-effect [30-34]. Dy3+-doped glasses are favorable for W-LEDs

applications comparing with the other rare earth ions. Dy3+ ion exhibit two intense

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emissions in blue and yellow regions. The combining of these emissions (yellow and

blue) bands create white light color which can be adjusted by changing the

composition concentration as well as the exciting wavelengths [44,45]. Further, Pr3+-

doped glasses show intense wavelength emissions in the red region [46]. Moreover,

the closeness of ladder-like energy levels of Dy3+ and Pr3+ ions enables the mutual

energy transfer between them. So, the optical properties can be adjusted by doping

with different concentrations of these ions to get a white light in addition to other

colors emission. Accordingly, the Er3+, Pr3+/ Dy3+ singly and doubly doped glasses

can be used for optical fiber amplification (communication field) as well as the SSL

applications were they have special spectral characteristics, emission intensity and

mutual energy transfer among them [48-51].

1.4 Aim and Objectives

In the Vis.-NIR region, new potential candidate glasses of Pr3+, Er3+/ Dy3+ ions singly

and doubly doped borotellurite glasses have been investigated for SSL, W-LEDs and

optical fiber laser application. The main objectives of this thesis can be concluded as

follows:

(i). To evaluate a new suitable borotellurite host glass by means of structural,

thermal, and optical properties to be doped with Pr3+, Er3+ and Dy3+ ions for

SSL and fiber laser applications.

(ii). To investigate Visible and NIR light emissions of Er3+ and Dy3+ singly and

codoped borotellurite glasses with different concentrations in terms of

thermal, structural, and optical properties.

(iii). To study the mutual energy transfers between Er3+ and Dy3+.

(iv). To explore the visible light emissions of Pr3+ and Dy3+ singly and codoped

borotellurite glasses with different concentrations of Pr3+ and their effects on

the thermal, structural, and optical properties.

(v). To determine and analyze the mutual energy transfers between Pr3+ and Dy3+.

1.5 Thesis Outlines

This thesis shows how to investigate and analyze the RE3+ ions doped and codped

glasses to employ them for suitable applications. The thesis organization is as follows:

Chapter 1 presents the overview of optical materials based on oxide glasses and their

structural, thermal, and optical features for different applications. Additionally, RE3+

ions doped optical glasses were reviewed based on their features in solid-state lighting.

Moreover, the problem statement and the main objectives of this thesis are also

included.

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Chapter 2 introduces the literature review about glass-forming fundamental

information. Glass formers, such as borate and tellurite glasses are reviewed where

they play an important role in optical materials like glasses. Also, the rare earth ion

such as Dy3+, Pr3+ and Er3+ in addition to some modifiers are discussed in detail where

these elements are employed to achieve our goals and objectives of this study.

Chapter 3 presents the properties of the RE3+ ions and some of their fundamental

characteristics, which are valuable resources in this thesis particularly for the role of

RE3+ ions in the borotellurite glass host. In the beginning, the basic RE3+ spectroscopic

theory is presented, which is considered for the recorded absorption spectra of the rare-

earth ions in solids. This is followed by the energy level scheme of rare-earth ions and

demonstration of the hypersensitive transitions along with transition probabilities,

radiative and non-radiative transition. Also, in this chapter ion-ion interaction is

discussed by means of cross-relaxation (CR), up-conversion energy transfers and

fluorescence quenching effect in rare-earth ions. Moreover, parameters were effects

the transition decay lifetime are discussed such as spontaneous emission, self-

absorption and phonon decay. Lastly, the Judd-Offelt theory is discussed from the

point of the analysis of the parameters.

Chapter 4 highlight the methodology of the glass sample preparation and

characterizations. The important steps of glass preparation procedures are described

here. Starting with glass sample calculations, followed by batching procedure, and

glass fabrication are clearly explained systematically. The material characterizations

by means of structural, thermal and optical analysis in addition to the instrumentation

are also specified.

Chapter 5, investigates the suitability of the glasses for potential application by using

doping technique of rear earth ions such as Dy3+, Pr3+ and Er3+, and that being divided

into two sections. Firstly, section 5.1 presents the structural, thermal, and optical

properties of borotellurite glasses introduced with Er3+/Dy3+singly and doubly doped

with deferent concentrations. As a result, it shows that all those glasses have similar

structural, thermal properties on contrary in optical features. Finally, section 5.2

presents Pr3+/ Dy3+ doped and codoped borotellurite glasses with deferent

concentrations. In this section, structural and thermal properties of the samples are

almost similar but the optical features can be tuned by changing excitation

wavelengths as well as the concentrations of the ions.

Chapter 6 concludes the findings of this study. Upon the analysis of the results, each

sample is identified for suitable applications like solid stat lighting or optical fiber

communication system (NIR laser amplifier system).

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