Spectroscopic properties of Er3+ doped germanate glasses before and after a heat treatment process

In this paper structural, thermal and optical properties of Er3+ doped germanate glasses with the composition of 63.0GeO2-9.8Ga2O3-11.1BaO-4.9X-8.8Na2O-2.5Er2O3 (in mol%), where X = ZnO, TiO2, Al2O3 and Y2O3 are reported. The investigated glasses exhibit low phonon energies (<1000 cm−1) and high glass transition temperature varying between 588 and 642 °C. The Raman spectra evidence about different polymerization degree of the glasses. The thermal treatment leads to the precipitation of various crystals, the composition of which depends on the glass composition. According to the spectroscopic properties Er3+ ions are suspected to have similar local environment in the as-prepared glasses. However, Er-doped crystals are expected to precipitate upon devitrification, which leads to significant change of the spectroscopic properties, in particular increase in the intensity of upconversion and MIR emissions is observed. It is demonstrated that the glasses with Y2O3, ZnO and TiO2 are promising glasses especially for MIR applications.publishedVersionPeer reviewe

Sinkkioksidin lisäämisen vaikutus hopeananopartikkelien muodostumiseen Er3+ doupatuissa fosfaattilaseissa

The purpose of this thesis was to investigate the impact of the glass composition on the formation of Ag nanoparticles in Er3+ doped phosphate glasses. The first task was to prepare Er3+ doped oxyfluoride phosphate glasses with varying glass compositions and to study the effect of the composition on the physical, structural, optical and spectroscopic properties of the glass. Glasses with the composition ((97x)*0.9NaPO3-(97-x)*0.1NaF-xZnO-2.5Ag2SO4-0.5Er2O3) with x =0, 1.25, 2.5, and 5 in mol% were prepared by standard melt quenching route. The glasses were melted in a quartz crucible for 5 minutes at temperatures ranging between 800°C and 875°C, depending on the glass composition and then annealed. Based on the DTA, all of the glasses are thermally stable as evidenced by their large T=Tx-Tg. The addition of ZnO increases the glass density and Tp, the crystallization temperature. Using IR and Raman spectroscopies, Zn is suspected to act as a modifier, leading to a depolymerization of the phosphate network and to a less cross-linked network. The addition of Zn increases the intensity of the emission band at 1.5 µm under pumping at 980nm although it has no noticeable impact on the site of Er3+. The second task was to grow silver nanoparticles (NPs) in the glasses using heat and to study the impact of the nanoparticles on the spectroscopic properties of the glasses. In order to grow silver NPs, the glasses were heat treated at a temperature of 10°C and 20°C above their respective glass transition temperature for 17 hours. The heat treatment changes the color of the glasses from pink to yellowish and so leads to the appearance of a new absorption band at ~400nm. This new band corresponds to the surface plasmon resonance (SPR) absorption of silver nanoparticles (NPs). The addition of ZnO was found to increase the intensity of the absorption band indicating that Ag NPs form more easily in a more depolymerized phosphate network. An increase in the intensity of the emission peak at 1530 nm was observed after heat treatment at Tg + 10°C due to the local field induced by SPR of Ag NPs and the energy transfer from metallic NPs to RE -ions. However, it is shown here that an increase in the heat treatment temperature to Tg + 20°C increases the intensity of the surface plasmon resonance absorption band of silver NPs indicating that a larger amount of Ag NPs are formed. However, the heat treatment decreases the intensity of the emission probably due to the back energy transfer from the exited states of Er3+ to the silver NPs. Finally, the X-ray diffraction analysis of the Tg + 20°C heat treated glasses confirms that the heat treatment does not lead to crystallization of the glasses

Designing Optical Glasses and Glass-Ceramics for Mid-Infrared Sensing Application

The purpose of this thesis was to design new optical glasses and glass-ceramics that can be deposited to thin films to be used as a mid-infrared light source and waveguiding layer for sensing application. Thus, the goal was to develop new glass-based materials with strong emission at 2.7 µm, corresponding to the 4I11/2 → 4I13/2 transition of Er3+ under 980 nm laser excitation. Erbium doped germanate glasses with the composition (1-x/100)*(64.6GeO2-10Ga2O3-11.4BaO-9Na2O)-xEr2O3-5MO with MO=Al2O3, TiO2, Y2O3 and ZnO and with x=0, 1 and 2.5 (in mol%) were prepared by the melt-quenching technique. The analysis of the IR spectra showed a high OH content in the glasses which is detrimental for MIR emission. Indeed, the OH groups in glass lead to a non-radiative relaxation route to quench the 2.7 µm emission. 2.7 µm emission was detected from all of the 2.5 mol% erbium containing glasses. The glass-ceramics were obtained by heat treating the glasses at T_g+20°C for 17 h to create the nuclei followed by a heat treatment at T_p for 1h and 6h for the growth of the nuclei into crystals. All of the glasses crystallized upon heat treatment. The crystallization mechanism was identified to be surface crystallization. The heat treatment increased the intensity of the emission of the Y containing glasses at 1.5 and 2.7 µm due to the crystalline field effect as evidenced by the sharp peaks in the emission bands. The Y containing glass had the most connected glass network, lowest OH content and highest 2.7 µm emission. Electron beam physical vapor deposition was used to deposit thin film from the newly developed glass with MO=ZnO..The composition of the thin film was studied by X-ray photoelectron spectroscopy. Only Ge and Na were detected in the film. The original target and the deposited film were deemed unsuitable for the application, more deposition trials are needed to achieve thin films with similar luminescent properties as the target

Designing Optical Glasses and Glass-Ceramics for Mid-Infrared Sensing Application

The purpose of this thesis was to design new optical glasses and glass-ceramics that can be deposited to thin films to be used as a mid-infrared light source and waveguiding layer for sensing application. Thus, the goal was to develop new glass-based materials with strong emission at 2.7 µm, corresponding to the 4I11/2 → 4I13/2 transition of Er3+ under 980 nm laser excitation. Erbium doped germanate glasses with the composition (1-x/100)*(64.6GeO2-10Ga2O3-11.4BaO-9Na2O)-xEr2O3-5MO with MO=Al2O3, TiO2, Y2O3 and ZnO and with x=0, 1 and 2.5 (in mol%) were prepared by the melt-quenching technique. The analysis of the IR spectra showed a high OH content in the glasses which is detrimental for MIR emission. Indeed, the OH groups in glass lead to a non-radiative relaxation route to quench the 2.7 µm emission. 2.7 µm emission was detected from all of the 2.5 mol% erbium containing glasses. The glass-ceramics were obtained by heat treating the glasses at T_g+20°C for 17 h to create the nuclei followed by a heat treatment at T_p for 1h and 6h for the growth of the nuclei into crystals. All of the glasses crystallized upon heat treatment. The crystallization mechanism was identified to be surface crystallization. The heat treatment increased the intensity of the emission of the Y containing glasses at 1.5 and 2.7 µm due to the crystalline field effect as evidenced by the sharp peaks in the emission bands. The Y containing glass had the most connected glass network, lowest OH content and highest 2.7 µm emission. Electron beam physical vapor deposition was used to deposit thin film from the newly developed glass with MO=ZnO..The composition of the thin film was studied by X-ray photoelectron spectroscopy. Only Ge and Na were detected in the film. The original target and the deposited film were deemed unsuitable for the application, more deposition trials are needed to achieve thin films with similar luminescent properties as the target

Sinkkioksidin lisäämisen vaikutus hopeananopartikkelien muodostumiseen Er3+ doupatuissa fosfaattilaseissa

The purpose of this thesis was to investigate the impact of the glass composition on the formation of Ag nanoparticles in Er3+ doped phosphate glasses. The first task was to prepare Er3+ doped oxyfluoride phosphate glasses with varying glass compositions and to study the effect of the composition on the physical, structural, optical and spectroscopic properties of the glass. Glasses with the composition ((97x)*0.9NaPO3-(97-x)*0.1NaF-xZnO-2.5Ag2SO4-0.5Er2O3) with x =0, 1.25, 2.5, and 5 in mol% were prepared by standard melt quenching route. The glasses were melted in a quartz crucible for 5 minutes at temperatures ranging between 800°C and 875°C, depending on the glass composition and then annealed. Based on the DTA, all of the glasses are thermally stable as evidenced by their large T=Tx-Tg. The addition of ZnO increases the glass density and Tp, the crystallization temperature. Using IR and Raman spectroscopies, Zn is suspected to act as a modifier, leading to a depolymerization of the phosphate network and to a less cross-linked network. The addition of Zn increases the intensity of the emission band at 1.5 µm under pumping at 980nm although it has no noticeable impact on the site of Er3+. The second task was to grow silver nanoparticles (NPs) in the glasses using heat and to study the impact of the nanoparticles on the spectroscopic properties of the glasses. In order to grow silver NPs, the glasses were heat treated at a temperature of 10°C and 20°C above their respective glass transition temperature for 17 hours. The heat treatment changes the color of the glasses from pink to yellowish and so leads to the appearance of a new absorption band at ~400nm. This new band corresponds to the surface plasmon resonance (SPR) absorption of silver nanoparticles (NPs). The addition of ZnO was found to increase the intensity of the absorption band indicating that Ag NPs form more easily in a more depolymerized phosphate network. An increase in the intensity of the emission peak at 1530 nm was observed after heat treatment at Tg + 10°C due to the local field induced by SPR of Ag NPs and the energy transfer from metallic NPs to RE -ions. However, it is shown here that an increase in the heat treatment temperature to Tg + 20°C increases the intensity of the surface plasmon resonance absorption band of silver NPs indicating that a larger amount of Ag NPs are formed. However, the heat treatment decreases the intensity of the emission probably due to the back energy transfer from the exited states of Er3+ to the silver NPs. Finally, the X-ray diffraction analysis of the Tg + 20°C heat treated glasses confirms that the heat treatment does not lead to crystallization of the glasses

Impact of ZnO addition on Er3+ near-infrared emission, the formation of ag nanoparticles, and the crystallization of sodium fluorophosphate glass

The impact of the progressive addition of ZnO up to 5 mol% on the thermal, structural, and optical properties of Er3+-doped phosphate glasses within the system NaPO3-NaF-ZnO-Ag2O is discussed. The glass network was found to depolymerize upon the addition of ZnO. This promotes a slight increase in the intensity of the emission at 1.5 μm as well as enhances the silver ions clustering ability under the heat treating. The Ag-nanoparticles formed after moderate heat-treatment can further enhance the emission at 1.5 μm, whereas an excessive amount of the clusters leads to the opposite effect. The addition of ZnO helps to slightly increase the glass ability of the system. The crystallization behavior study revealed that surface crystallization is observed for all the glasses. It is found that even a small ZnO addition changes the crystalline phases formed after devitrification. Moreover, the addition of ZnO decreases the crystallization tendency of the glass.publishedVersionPeer reviewe

Impact of Ag2O Content on the Optical and Spectroscopic Properties of Fluoro-Phosphate Glasses

Glasses with the system (84.60-x) NaPO3-5 ZnO-(9.40-x) NaF-x Ag2O-1 Er2O3, (x = 0, 2, 4, and 6) (mol%) were synthesized by the conventional melt-quenching method. The impact of the addition of Ag2O on the physical, thermal, structural, and optical properties of the glasses is discussed. The Judd-Oflet analysis was used to evaluate the radiative properties of the emission transitions of the glasses. The enhancement of luminescence properties due to Ag2O is discussed in terms of consequent changes in the local electromagnetic field, symmetry, and the ligand field around the Er3+ ion. The heat treatment of the glass was performed in order to precipitate Ag nanoparticles (NPs), which form as a layer at the surface of the heat-treated glasses as confirmed using scanning electron microscopy (SEM). The Ag NPs were found to increase the intensity of the emission at 1.5 µm.publishedVersionPeer reviewe