Transition metal ion doped phosphors for optical temperature sensing
- Abstract
- 3d3 transition metal ion Mn4+ doped phosphors are renewed optical materials for application in warm white light diodes (LEDs) as the red component, which have been extensively investigated recently. Mn4+ ions are known as activators in the oxide and fluoride hosts that exhibit efficient red efficient sharp or band luminescence in the spectral range of 600 - 700 nm. All the Mn4+ doped materials shown broadband absorption in the range of 250 nm - 600 nm, which is matched well with the commercial 365 nm ultraviolet (UV) or 460 nm blue LEDs. The unique optical properties of Mn4+ are attributed to the distinct electronic structure of Mn4+. The luminescence of Mn4+ ions usually found on the octahedral sites of solids and strongly depends on the point symmetry of the cation site in the lattices. In an octahedral environment, the luminescence properties of Mn4+ are dominated by the crystal field strength and influenced by the nephelauxetic effect, which depend on the nature of the surrounding ligands, chemical bond lengths and angles between chemical bonds. Several groups and researchers have investigated the luminescent properties of Mn4+ in diverse hosts by tailoring the crystal structure to obtain optimal luminescence efficiency and applied the Mn4+ doped phosphors in wLEDs. However, most studies are focused on the fluoride or oxide host to explore the application in wLEDs and planting illustration, few works have been attended on other types of hosts and application.
The aim of this study is to investigate the novel suitable host candidate for Mn4+ doping and extend the application toolbox of Mn4+ doped luminescence materials. In this study, two types of oxyfluoride hosts Cs2WO2F4 and Na2WO2F4 and one kind of double perovskite Y2MgTiO6 oxide host were introduced to serve as host materials for Mn4+ doping. The synthesis, crystal structure, optical properties and the optical temperature sensing features are comprehensively demonstrated.
From this study, it is found that the relationship between the anti-Stoke and Stokes vibrational sidebands of spin-forbidden 2Eg 4A2g red emission of Mn4+ obeys the Boltzmann thermal population low. Based on the fluorescence intensity ratio (FIR) technique, the optical temperature sensitivities are confirmed as 2.1x10-3 K-1 at 167 K for Cs2WO2F4, 6.58x10-3 K-1 at 193 K for Na2WO2F4 and 1.42x10-3 K-1 at 153 K for Y2MgTiO6, respectively. Our studies exhibit that the commercial UV or blue chips fabricated Mn4+ doped phosphors are potential non-contact optical thermometry materials in cryogenic environment.
- Issued Date
- 2018
- Awarded Date
- 2018. 8
- Type
- Dissertation
- Publisher
- 부경대학교
- Affiliation
- 부경대학교 대학원
- Department
- 대학원 의생명기계전기융합공학협동과정
- Advisor
- 서효진
- Table Of Contents
- List of Figures iv
List of Tables vi
Abstract vii
1. Introduction 9
1.1. Background 9
1.1.1. Luminescent materials 9
1.1.2. Absorption, emission and configurational coordinate diagram 10
1.1.3. Decay of luminescence 12
1.1.4. Energy transfer 13
1.1.5. Transition metal ions 16
1.1.6. Crystal field theory and nephelauxetic effect 18
1.1.7. Optical temperature sensing 23
1.1.7.1. Strategies of optical sensing 23
1.1.7.2. Boltzmann law 24
1.2. Scopes and outline of this thesis 27
2. Luminescence, energy transfer and optical thermometry of a novel narrow red emitting phosphor: Cs2WO2F4:Mn4+ 28
2.1. Introduction 28
2.2. Experimental section 29
2.2.1. Preparations 29
2.2.2. Characterization 30
2.3. Results and discussion 31
2.3.1. Structure, morphology and composition 31
2.3.2. Photoluminescence studies 34
2.3.2.1. Temperature dependent luminescence properties of pure Cs2WO2F4 34
2.3.2.2. Room temperature luminescence of Mn4+ doped Cs2WO2F4 37
2.3.2.3. Optical thermometry of Cs2WO2F4: 5%Mn4+ 43
2.3.2.4. Luminescence dynamics in Cs2WO2F4: 5%Mn4+ 47
2.3.2.5. Energy transfer in Cs2WO2F4:Mn4+ under the UV excitation 49
2.4. Summary 54
3. Excitation power dependent optical temperature behaviors in Mn4+ doped oxyfluoride Na2WO2F4 55
3.1. Introduction 55
3.2. Characterization 57
3.3. Results and discussion 57
3.3.1. Phase identification and crystal structure 57
3.3.2. Photoluminescence studies 59
3.3.2.1. Room temperature luminescence properties 59
3.3.2.2. Temperature dependent luminescence properties 64
3.3.2.3. Temperature dependent luminescence properties with different power and pump sources 65
3.3.2.4. Temperature dependent optical thermometry with different power density and pump sources 68
3.4. Summary 77
4. Optical thermometry based on vibration sidebands in Y2MgTiO6:Mn4+ double perovskite 78
4.1. Introduction 78
4.2. Experimental section 79
4.2.1. Preparations 79
4.2.2. Characterization 80
4.3. Results and discussion 81
4.3.1. Phase formation and structure characteristics 81
4.3.2. Luminescence properties of Y2MgTiO6: Mn4+ 86
4.3.3. Application of Y2MgTiO6:Mn4+ in optical temperature sensing 95
4.4. Summary 98
5. Conclusions and future works 99
5.1. Conclusions 99
5.2. Future works 100
6. Reference 101
Acknowledgments 106
- Degree
- Doctor
- Appears in Collections:
- 대학원 > 4차산업융합바이오닉스공학과
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