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URN etd-0909110-133203 Statistics This thesis had been viewed 2469 times. Download 780 times. Author Chih-Chun Chiang Author's Email Address No Public. Department Materials Engineering Year 2009 Semester 2 Degree Ph.D. Type of Document Doctoral Dissertation Language zh-TW.Big5 Chinese Page Count 187 Title EFFECTS OF RARE EARTH DOPING ON THE MICROSTRUCTURE AND LUMINESCENCE CHARACTERISTICS OF GLASS Keyword Photoluminescence Rare Earth Microstructrue Glass Glass Microstructrue Rare Earth Photoluminescence Abstract In recent years, luminescent glass materials have attracted great attention, especially application for the solid state laser and amplifier devices. In various glass systems, phosphate glass has been widely studied because of it has high solubility of rare earth and low melting/forming temperatures. Moreover, some literatures reported that formation of microstructure in the glass matrix can change the environment of rare earth (such as in glass and crystalline phase). Photoluminescence intensity can be enhanced due to the light-scattering effect in the microstructural glass, which increases the population of rare earth ion on the high energy level. The purpose of this study is to explore the luminescence characteristic of the microstructural borosilicate and phosphate glasses doped with high content rare earth. The results are as follows:
(a) Compositional Dependence of Phase Separation and Photoluminescence in Rare Earths-Doped Sodium Borosilicate Glasses
In this study, the effects of the kind of rare earth (Er, Eu, and Nd), rare earth concentration (up to 3 mole%), and P2O5 addition (0 and 2 mole%) on the phase separation, optical absorption, and photoluminescence (PL) of the sodium borosilicate glasses were investigated. It was found that adding P2O5, increasing rare earth content and changing the kind of rare earth can enhance the phase separation of Na2O- B2O3-SiO2 glass. Adding P2O5 results in the simultaneous segregation of rare earth and P in sodium phosphate droplets. As a consequence, rare earth-bearing phosphate crystals developed within the droplets. Development of the droplet phase enhances both the light-scattering effect (enhancing the PL intensity) and the concentration quenching effect (reducing the PL intensity).
(b) Compositional Dependence of Phase Separation and Photoluminescence in Er3+-Doped Alkali Borosilicate Glasses
In this study, the effects of the kind of alkali (Li, Na, and K), Er2O3 concentration (up to 3 mol%), and P2O5 addition (0 and 2 mole%) on the phase separation, optical absorption, and photoluminescence (PL) of the alkali borosilicate glasses were investigated. The relationship between microstructure and optical properties of the glasses is discussed. It was found that the development of the droplet phase enhances both the light-scattering effect (enhancing the PL intensity) and the concentration quenching effect (reducing the PL intensity). As a result, the variation of the PL intensity of the Er3+ 4I13/2 - 4I15/2 transition with Er2O3 content is mainly caused by the conflict between the light-scattering effect and the concentration-quenching effect. The 1 mole% Er2O3-doped, P2O5-containing, sodium borosilicate glass has the optimum microstructure and thus the highest PL intensity.
(c) Effects of Er3+ Doping on the Structure, Thermal Properties, and Crystallization Behavior of SnO-P2O5 Glass
In this study, a new type of Er2O3–doped SnO–P2O5 glass with Er2O3 content of 0 – 8 mole% has been obtained. It was found that physical properties, thermal properties, and crystallization behavior of the glass exhibit discontinuities at Er2O3 content of 2 – 4 mole%. It was also noted that reheating the glass at 375°C, which is higher than the dilatometric softening temperature, results in the crystallization of a tin phosphate phase from glass surface when Er2O3 content is ≤ 0.5 mole%, resulting in serious cracking of the glass. Adding more Er2O3 (1 – 8 mole%) totally suppresses the surface crystallization, thus it is helpful to glass shaping processes.
(d) Photoluminescence Characteristics of Er3+ Doped and Er3+/Yb3+ Co-Dpoed SnO-P2O5 Glass
In this study, effects of Er2O3 (0 – 8 mole%) doping and Er2O3 and Yb2O3 co-doping (total 1 – 7 mole%) on the absorption cross-section, PL, and upconversion intensities of the SnO-P2O5 glass have been investigated. Precipitation of ErPO4 and (Yb, Er)PO4 crystalline phase in the SnO-P2O5 glass matrix when the total rare-earth oxide content is > 4 mole% plays an important role in determining the absorption cross-section, PL, and upconversion intensities. For Er3+-doped glass, the variation of PL characteristic with the Er2O3 content is obviously different from that for general rare-earth-doped glasses. This result is explained in terms of the light-scattering effect caused by the ErPO4 crystals and the constant Er-Er distance in ErPO4 crystals with the increasing Er2O3 content. After co-doping with Yb2O3, the PL intensity of the glass is enhanced by about 14.7 times at the optimum Yb2O3 content of 6 mole% (~1.81×1021 ions/cm3). Further increase in the Yb2O3 content results in the reduction of PL intensity which can be explained in terms of the APTE upconversion effect.
(e) Effects of Er3+ Doping on the Structure, Thermal Properties, and Photoluminescence Characteristics of ZnO-P2O5 Glass
In this study, Er2O3–doped ZnO–P2O5 glass with Er2O3 content of 0 – 4 mole% has been obtained. It was found that the fraction of Q0 (orthophosphate)-Q1 (pyrophosphate) structure increase in ZnO-P2O5 glass with the Er2O3 content increased. When Er2O3 content is 4 mole%, crystalline particles of ErPO4 have precipitated within the ZnO-P2O5 glass matrix. The physical and thermal properties of the glass linearly increased with increasing Er2O3 content. According to the result, absorption cross-section and PL intensity of the ZnO-P2O5 glass are higher than that of SnO-P2O5 glass, because of the ZnO-P2O5 glass has high ionic packing ratio which reduces the covalency of Er-O bond, and then increases the spontaneous emission probabilities. This result does not conform to the expectation, namely the stimulated emission cross-section of laser glass does not increase with the increasing refractive index.
Advisor Committee Jiin-Jyh Shyu - advisor
Files Date of Defense 2010-07-28 Date of Submission 2010-09-09