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Synthesis of YVO4:Eu3+ phosphors and the effect of nano-sized SiO2 on the optical properties

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dc.contributor.advisor강신후-
dc.contributor.author마흐디-
dc.date.accessioned2017-10-27T16:40:07Z-
dc.date.available2017-10-27T16:40:07Z-
dc.date.issued2017-08-
dc.identifier.other000000145637-
dc.identifier.urihttps://hdl.handle.net/10371/136781-
dc.description학위논문 (박사)-- 서울대학교 대학원 공과대학 재료공학부, 2017. 8. 강신후.-
dc.description.abstractIn this work, bulk sized YVO4:Eu3+ phosphor was synthesized via simple solid state method in air atmosphere at 1100 °C, which has a variety of applications in the fields of lighting and solar cells. All these applications are possible due to the proper designation of particle size, morphology and defects control of surface
through the experimental parameters. Referring to the literatures, synthesis of the YVO4:Eu3+ phosphors in the air atmosphere, results in the formation of many defects and then the optical properties are suppressed. For improvement of luminescence properties, the surface of YVO4:Eu3+ phosphor was coated by a thin layer of SiO2 through sol-gel (with a source of TEOS) and then obtained
morphology and photoluminescence properties were investigated in details. It was found that silica coating yields an increase in luminescence intensity of the YVO4:Eu3+ phosphors due to the reduction of reflection of excitation light and the maximum amounts of emission intensity was obtained with 1 wt% silica coating when the thickness of silica on the surface is in the range of 20-50 nm.
Another effective mechanism for luminescence improvement is the decrease of surface defects by coating the surface of phosphor. The ESR analyses approved that with coating of a layer of silica on the surface of YVO4:Eu3+ phosphor, the amounts of oxygen vacancy defects reduced remarkably. Furthermore, the coating of YVO4:Eu3+ phosphors by silica enhanced the chemical and thermal stability too. Also, in another procedure and to study the effect of SiO2 core on YVO4:Eu3+ phosphors, the YVO4:Eu3+@SiO2 phosphors were synthesized through sol-gel process too. It was found that after 5 times coating of YVO4:Eu3+ on SiO2 core, the emission intensity is significantly comparable to that of pure YVO4:Eu3+ phosphors. In addition, although the coating of YVO4:Eu3+@SiO2 phosphors with silica resulted in decrease of luminescence properties but the thermal quenching and chemical stability were enhanced.		-
dc.description.tableofcontentsI. Introduction 1
1.1.Phosphors at a glance 1
1.1.1. Synthesis of phosphors 2
1.2.YVO4 phosphors 3
II. Synthesis of Bulk YVO4: Eu3+ Phosphor Materials 6
2.1. Introduction 6
2.2. Experimental 7
2.2.1. Preparation 7
2.2.2. Characterization 7
2.3. Results and discussion 8
2.3.1. XRD, SEM, HRTEM Studies 8
2.3.2. PL Analysis 10
2.3.2.1. Un-doped YVO4 phosphor 10
2.3.2.2.YVO4: Eu3+ phosphor .12
2.3.3. Raman Analysis.. 18
2.4. Summary and Conclusion 20
III. Coating of YVO4: Eu3+ phosphors with silica 21
3.1. Introduction 21
3.2.Experimental 26
3.2.1. Preparation 26
3.2.1.1. YVO4: Eu3+ Phosphors Synthesis 26
3.2.1.2. Coating of YVO4: Eu3+ phosphors with silica 26
3.2.2. Characterization 28
3.3.Results and discussion 28
3.3.1. XRD Analysis 28
3.3.2. FESEM Observations 30
3.3.3. TEM Observations 35
3.3.4. XPS Analysis .8
3.3.5. FT- IR Analysis 43
3.3.6. PL Analysis 45
3.3.6.1. Reflection 47
3.3.6.2. Quantum Yield 50
3.3.7. Chemical Stability 52
3.3.7.1. Water Degradation .52
3.3.7.2. Acid Degradation 56
3.3.8. Thermal quenching 59
3.3.9. ESR Analysis 64
3.4. Summary and conclusion 66
IV. Core shell YVO4:Eu3+@SiO2 phosphors 67
4.1 Introduction 67
4.2. Experimental 69
4.2.1. Synthesis of silica cores 69
4.2.2. Synthesis of SiO2@Y0.96Eu0.04VO4 core–shell phosphors 69
4.3. Results and discussion 72
4.3.1. XRD Analysis 72
4.3.2. FESEM Observations 74
4.3.3. HRTEM Observations 76
4.3.4. FT- IR Analysis 78
4.3.5. PL Analysis 80
4.3.6. SiO2 coated YVO4:Eu3+@SiO2 phosphors 84
4.3.6.1. XRD Analysis 85
4.3.6.2. FESEM Observation 86
4.3.6.3. HRTEM Observation 87
4.3.6.4. PL Analysis 89
4.3.6.5. Chemical Stability.. 90
4.3.6.6. Thermal quenching 92
4.4. Summary and conclusion 95
V. Overall Conclusion 96
Appendix 98
References 99
Acknowledgement 110		-
dc.formatapplication/pdf-
dc.format.extent6604277 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectLuminescence-
dc.subjectSilica-
dc.subjectsolid state-
dc.subjectsol-gel-
dc.subjectexcitation-
dc.subjectemission-
dc.subject.ddc620.1-
dc.titleSynthesis of YVO4:Eu3+ phosphors and the effect of nano-sized SiO2 on the optical properties-
dc.typeThesis-
dc.contributor.AlternativeAuthorSeyed Mahdi Rafiaei-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 재료공학부-
dc.date.awarded2017-08-
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