稀土掺杂Gd基上转换荧光粉体的制备与发光性能研究
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摘要
上转换发光材料是在长波长激发下,发出短波长的一种发光材料。它们大多属于稀土掺杂的无机材料。稀土离子掺杂的上转换发光材料在三维立体显示、红外辐射探测、商标激光防伪等领域有着广泛的应用前景,近年来已成为国内外发光材料的研究热点。
稀土Er~(3+)离子具有丰富的能级结构,并且容易通过其它离子的敏化作用而提高上转换发光效率。加入敏化剂实现敏化发光是提高上转换发光效率的一种有效方法。Yb~(3+)离子具有独特的双能级结构,能敏化Er~(3+)离子,是一种很好的敏化剂,从而能极大提高其上转换发光效率。
氧化钆(Gd_2O_3)和钆铝氧化物(Gd_3Al_5O_(12))由于具有优异的物理化学性质和稳定的立方晶体结构,作为基质材料在发光材料领域具有良好的应用前景。基于此,本论文选择Gd_2O_3和Gd_3Al_5O_(12)两种钆基氧化物作为研究对象,用热重-示差扫描量热分析(TG-DSC)、X射线粉末衍射分析(XRD)、红外光谱分析(FTIR)、扫描分析(SEM)和上转换荧光光谱分析等方法,系统研究了Er~(3+)、Yb~(3+)稀土离子掺杂体系的制备与光谱性能。
采用共沉淀法制备了Er~(3+)单掺杂以及Er~(3+)/Yb~(3+)双掺杂的Gd_2O_3粉体,研究了煅烧温度对发光材料的结构、形貌、尺寸以及上转换发光特性的影响。结果表明:获得的粉体结构均为单一的立方相结构,随着煅烧温度的升高,结晶度越来越高,红、绿上转换发射都增强。同时证明了Yb~(3+)的掺入能够大大提高粉体的上转换发光效率;同时揭示了Er~(3+)/Yb~(3+)共掺杂Gd_2O_3粉体的上转换发光机制,指出绿色和红色上转换发光均为双光子上转换吸收过程。
采用改进的共沉淀法制备了Er~(3+)/Yb~(3+)双掺杂Gd_2O_3粉体,即:向溶液中添加了一定量的乙醇,研究了煅烧温度、溶剂对稀土掺杂Gd_2O_3粉体的结构、形貌及上转换发光特性的影响。结果表明:采用此方法制得的粉体为单一的立方相结构,通过SEM照片观察:当900oC煅烧后,粉体颗粒分散性良好,粒度均一,尺寸在2μm左右,形貌呈规则的齿形。随着煅烧温度的升高,颗粒形貌呈松散的薄片状。从上转换发光光谱图上可以看出:添加乙醇以后,样品的主发射为红色上转换发射,而未添加乙醇制得的样品的主发射为绿色上转换发射,且在同一温度下煅烧,添加乙醇制备的样品的上转换发光强度相比之下要高得多。
采用共沉淀法制备了Er~(3+)/Yb~(3+)双掺杂Gd_3Al_5O_(12)粉体,研究了煅烧温度、沉淀剂的浓度对稀土掺杂Gd_3Al_5O_(12)粉体的结构、形貌及上转换发光特性的影响。结果表明:当碳酸氢铵与金属总离子的摩尔浓度比值为7时,在较低的煅烧温度和较短的煅烧时间下(1100oC,2h)即可获得石榴石型结构的Gd_3Al_5O_(12):Er~(3+)/Yb~(3+)粉体;同时,荧光光谱分析也表明,在该条件下获得的Gd_3Al_5O_(12):Er~(3+)/Yb~(3+)粉体在980nm半导体激光器(LD)激发下获得的发光性能最好。
Up-conversion luminescence materials are one kind of light-emitting materials with the feature that emitting short wavelength photons after excited with long wavelength photons. Most of them are rare earth doped materials. These up-conversion luminescence materials have been intensively studied due to their potential applications in many fields, such as three-dimensional displays, infrared radiation detectors, and laser anti-counterfeiting brands. This kind of materials has become a research focus at home and abroad in recent years.
Er~(3+) ion has not only a rich energy-level structure but also can easily realize up-conversion efficiency when sensitized by other rare earth ions. In particular, this ion is a good activator with Yb~(3+) as a sensitizer in up-conversion luminescence materials when pumped by 980 nm LD. Yb~(3+) ion has a unique two-level structure, and Er~(3+) ion is in accordance with the energy matching of the gap (between 2F11/2 and 2F5/2) of Yb~(3+), so it can improve the up-conversion efficiency.
Both Gd_2O_3 with cubic phase and garnet-structural Gd_3Al_5O_(12) have favorable physical and chemical properties, so they are promising luminescent hosts in many optical applications. Thus this research chose these two Gadolinium-based oxides (Gd_2O_3, Gd_3Al_5O_(12)) as the research object, and the preparation and luminescence properties of the Er~(3+)/Yb~(3+) co-doped Gd_2O_3 and Gd_3Al_5O_(12) were systematically investigated by Fourier transform infrared spectroscopy (FTIR), Thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM) and up-conversion emission measurement.
Er~(3+) doped and Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders have been prepared by the co-precipitation method. It’s mainly discussed the effects of sintering temperatures on the size, structure, morphology and up-conversion luminescence properties of the powders. It was shown that the structures of the powders were all pure cubic phase. It’s also found that the crystallinity increased as the heat-treat temperature rising. Moreover, both red and green up-conversion emissions were enhanced. It’s proved that the up-conversion luminescence efficiency can be improved greatly by doping Yb~(3+) as the sensitizer. It was also explored the up-conversion emission mechanism of Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders were attributed to two-photon absorption up-conversion process.
Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders had been also prepared by the modified co-precipitation method. This method was modified by adding quantities of ethanol into the solution, and the effects of sintering temperatures and solvent (ethanol) on phase-structure, size, morphology and up-conversion emission properties were systematically investigated. It’s shown that the powders synthesized by this method were all pure cubic phase, and the powders had good diffusion with the size about 2μm and the morphology was regular zigzag when the heat-treatment temperature was 900oC. As the sintering temperature rising, the morphology of the particles seemed like loss slices. It can be seen from the up-conversion luminescence spectra that the main emission of the samples was red up-conversion, and the luminescent intensity of the powders prepared by the modified co-precipitation method was much stronger than that of the powders prepared by traditional co-precipitation method at the same sintering temperature. On the contrary, when ethanol was not added into the solvent, it can be found that the main emission of the samples was green up-conversion.
Er~(3+)/Yb~(3+) co-doped Gd_3Al_5O_(12) powders had been also prepared by the co-precipitation method, and the effects of sintering temperatures and the concentration of precipitant on the phase structure and up-conversion emission properties were systematically investigated. It’s found that the pure garnet structure GAG phase was obtained at lower sintering temperature and shorter heat-treatment time when the concentration ratio of NH4HCO3 to all the cations was 7. The photoluminescence spectra showed that the luminescent intensity of the powders was the strongest under the excitation of 980 nm LD.
稀土Er~(3+)离子具有丰富的能级结构,并且容易通过其它离子的敏化作用而提高上转换发光效率。加入敏化剂实现敏化发光是提高上转换发光效率的一种有效方法。Yb~(3+)离子具有独特的双能级结构,能敏化Er~(3+)离子,是一种很好的敏化剂,从而能极大提高其上转换发光效率。
氧化钆(Gd_2O_3)和钆铝氧化物(Gd_3Al_5O_(12))由于具有优异的物理化学性质和稳定的立方晶体结构,作为基质材料在发光材料领域具有良好的应用前景。基于此,本论文选择Gd_2O_3和Gd_3Al_5O_(12)两种钆基氧化物作为研究对象,用热重-示差扫描量热分析(TG-DSC)、X射线粉末衍射分析(XRD)、红外光谱分析(FTIR)、扫描分析(SEM)和上转换荧光光谱分析等方法,系统研究了Er~(3+)、Yb~(3+)稀土离子掺杂体系的制备与光谱性能。
采用共沉淀法制备了Er~(3+)单掺杂以及Er~(3+)/Yb~(3+)双掺杂的Gd_2O_3粉体,研究了煅烧温度对发光材料的结构、形貌、尺寸以及上转换发光特性的影响。结果表明:获得的粉体结构均为单一的立方相结构,随着煅烧温度的升高,结晶度越来越高,红、绿上转换发射都增强。同时证明了Yb~(3+)的掺入能够大大提高粉体的上转换发光效率;同时揭示了Er~(3+)/Yb~(3+)共掺杂Gd_2O_3粉体的上转换发光机制,指出绿色和红色上转换发光均为双光子上转换吸收过程。
采用改进的共沉淀法制备了Er~(3+)/Yb~(3+)双掺杂Gd_2O_3粉体,即:向溶液中添加了一定量的乙醇,研究了煅烧温度、溶剂对稀土掺杂Gd_2O_3粉体的结构、形貌及上转换发光特性的影响。结果表明:采用此方法制得的粉体为单一的立方相结构,通过SEM照片观察:当900oC煅烧后,粉体颗粒分散性良好,粒度均一,尺寸在2μm左右,形貌呈规则的齿形。随着煅烧温度的升高,颗粒形貌呈松散的薄片状。从上转换发光光谱图上可以看出:添加乙醇以后,样品的主发射为红色上转换发射,而未添加乙醇制得的样品的主发射为绿色上转换发射,且在同一温度下煅烧,添加乙醇制备的样品的上转换发光强度相比之下要高得多。
采用共沉淀法制备了Er~(3+)/Yb~(3+)双掺杂Gd_3Al_5O_(12)粉体,研究了煅烧温度、沉淀剂的浓度对稀土掺杂Gd_3Al_5O_(12)粉体的结构、形貌及上转换发光特性的影响。结果表明:当碳酸氢铵与金属总离子的摩尔浓度比值为7时,在较低的煅烧温度和较短的煅烧时间下(1100oC,2h)即可获得石榴石型结构的Gd_3Al_5O_(12):Er~(3+)/Yb~(3+)粉体;同时,荧光光谱分析也表明,在该条件下获得的Gd_3Al_5O_(12):Er~(3+)/Yb~(3+)粉体在980nm半导体激光器(LD)激发下获得的发光性能最好。
Up-conversion luminescence materials are one kind of light-emitting materials with the feature that emitting short wavelength photons after excited with long wavelength photons. Most of them are rare earth doped materials. These up-conversion luminescence materials have been intensively studied due to their potential applications in many fields, such as three-dimensional displays, infrared radiation detectors, and laser anti-counterfeiting brands. This kind of materials has become a research focus at home and abroad in recent years.
Er~(3+) ion has not only a rich energy-level structure but also can easily realize up-conversion efficiency when sensitized by other rare earth ions. In particular, this ion is a good activator with Yb~(3+) as a sensitizer in up-conversion luminescence materials when pumped by 980 nm LD. Yb~(3+) ion has a unique two-level structure, and Er~(3+) ion is in accordance with the energy matching of the gap (between 2F11/2 and 2F5/2) of Yb~(3+), so it can improve the up-conversion efficiency.
Both Gd_2O_3 with cubic phase and garnet-structural Gd_3Al_5O_(12) have favorable physical and chemical properties, so they are promising luminescent hosts in many optical applications. Thus this research chose these two Gadolinium-based oxides (Gd_2O_3, Gd_3Al_5O_(12)) as the research object, and the preparation and luminescence properties of the Er~(3+)/Yb~(3+) co-doped Gd_2O_3 and Gd_3Al_5O_(12) were systematically investigated by Fourier transform infrared spectroscopy (FTIR), Thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM) and up-conversion emission measurement.
Er~(3+) doped and Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders have been prepared by the co-precipitation method. It’s mainly discussed the effects of sintering temperatures on the size, structure, morphology and up-conversion luminescence properties of the powders. It was shown that the structures of the powders were all pure cubic phase. It’s also found that the crystallinity increased as the heat-treat temperature rising. Moreover, both red and green up-conversion emissions were enhanced. It’s proved that the up-conversion luminescence efficiency can be improved greatly by doping Yb~(3+) as the sensitizer. It was also explored the up-conversion emission mechanism of Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders were attributed to two-photon absorption up-conversion process.
Er~(3+)/Yb~(3+) co-doped Gd_2O_3 powders had been also prepared by the modified co-precipitation method. This method was modified by adding quantities of ethanol into the solution, and the effects of sintering temperatures and solvent (ethanol) on phase-structure, size, morphology and up-conversion emission properties were systematically investigated. It’s shown that the powders synthesized by this method were all pure cubic phase, and the powders had good diffusion with the size about 2μm and the morphology was regular zigzag when the heat-treatment temperature was 900oC. As the sintering temperature rising, the morphology of the particles seemed like loss slices. It can be seen from the up-conversion luminescence spectra that the main emission of the samples was red up-conversion, and the luminescent intensity of the powders prepared by the modified co-precipitation method was much stronger than that of the powders prepared by traditional co-precipitation method at the same sintering temperature. On the contrary, when ethanol was not added into the solvent, it can be found that the main emission of the samples was green up-conversion.
Er~(3+)/Yb~(3+) co-doped Gd_3Al_5O_(12) powders had been also prepared by the co-precipitation method, and the effects of sintering temperatures and the concentration of precipitant on the phase structure and up-conversion emission properties were systematically investigated. It’s found that the pure garnet structure GAG phase was obtained at lower sintering temperature and shorter heat-treatment time when the concentration ratio of NH4HCO3 to all the cations was 7. The photoluminescence spectra showed that the luminescent intensity of the powders was the strongest under the excitation of 980 nm LD.
引文
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