【作者】 方丽梅；

【导师】 祖小涛；

【作者基本信息】 电子科技大学 ， 光学， 2009， 博士

【摘要】 SnO2是一种重要的宽带隙n型半导体(禁带宽度为3.6 eV),其优异的光电和气敏性能,使得它在发光材料、吸光材料、催化剂、气敏元件、稀磁半导体、锂离子电池负极材料等领域具有广泛应用。通过纳米材料改性方法如控制制备工艺、掺杂和热处理过程,使SnO2纳米半导体材料的宏微观性能够得到明显改善,还可能出现一些新奇的特性,有望大大拓展其应用领域,因此研究金属离子改性的SnO2半导体纳米材料的制备和特性对于材料科学的基础研究和应用研究都具有重要的意义。本论文采用溶胶-凝胶法和水热法制备了过渡金属离子(Fe、Co、Mn)、稀土元素Ce、功能离子Zn掺杂的二氧化锡纳米颗粒,首次系统深入研究了制备方法、掺杂离子浓度和热处理温度对SnO2微结构和宏观性能的影响。主要的研究成果及创新点如下：1.首次同时采用了溶胶-凝胶法和水热法制备了Fe掺杂的SnO2纳米颗粒,并对两种方法制备的样品的微结构和性能进行了比较,择优选择水热法作为后续样品的制备方法。通过XRD、BET、HRTEM、FTIR、PL、DRS、MPMS等方法对样品的微结构和光学、磁学性能进行表征。结果表明,溶胶凝胶法和水热法制备的Fe掺杂SnO2纳米颗粒呈金红石型SnO2结构,大小均匀,分散性好。随Fe掺杂浓度增加和热处理温度升高,吸收光谱明显红移,所有样品分别在389 nm和470nm附近出现紫外发光峰和蓝色发光带。磁性研究表明样品以顺磁性为主。通过对两种方法制备的样品的微结构和性能进行比较,表明水热法无须焙烧即可直接合成Fe掺杂的SnO2纳米颗粒。对同一掺杂浓度和同样热处理温度的样品,水热法制备的纳米颗粒分散性更好、分布范围更窄、比表面积更大、热稳定性更好。因此接下来的研究样品采用水热法来制备。2.系统研究了过渡金属离子Co掺杂SnO2纳米颗粒的水热制备和掺杂浓度与热处理温度对纳米颗粒的微结构、光吸收、荧光特性和磁性能的影响。实验制备的样品粒径随掺杂浓度增加而减小,随热处理温度升高而增大。随因掺杂浓度增大引起的粒径减小,吸收边红移,紫外发光峰和蓝色发光峰的强度比减小。PPMS测试显示,样品呈现顺磁性,随焙烧温度升高,磁矩减小。3.采用水热法合成了不同掺杂浓度的Mn掺杂SnO2纳米颗粒,并通过不同的热处理过程来研究其热稳定性。通过对颗粒微结构和光学、磁学性能的研究发现,四方晶系金红石型Mn掺杂的SnO2纳米颗粒呈球形,随Mn掺杂浓度增大,粒径减小,吸收边红移,在389 nm和470 nm附近分别出现紫外发光峰和蓝色发光峰。经焙烧后,样品的粒径增大,紫外发光峰和蓝色发光峰强度减弱。并发现,Mn的掺杂并没有导致样品铁磁性的出现。4.将不同浓度的稀土元素离子Ce掺入到SnO2纳米颗粒中,并详细研究了样品的微结构和光学特性。水热法直接合成了四方相的金红石型Ce掺杂SnO2纳米颗粒,样品粒径随Ce掺杂量增加而减小,随焙烧温度升高而增大。所有样品都有紫外发光峰和蓝色发光峰,随Ce掺杂浓度增大和焙烧温度升高,发光峰位置不变。光学带隙随Ce掺杂浓度增加和焙烧温度升高而增大。5.系统研究了水热法制备的功能离子Zn掺杂的SnO2纳米颗粒的微结构和光学特性。Zn:Sn比例较小时,Zn掺杂并不改变晶体结构,但XRD衍射峰位略有右移,Zn:Sn摩尔比达到20：1时出现杂质相Zn2SnO4。随Zn:Sn比例增加,紫外可见漫反射光谱表现蓝移,光学带隙增大,位于389 nm附近的紫外发光峰无明显峰移,强度减弱。蓝色发光峰由未掺杂前的470 nm移到掺杂后的439 nm附近,强度随Zn:Sn比例增加而增强。经热处理后,相比于未热处理前,样品的吸收边移向低能端,蓝色发光峰红移。总之,探索制备方法、掺杂、热处理温度对纳米二氧化锡的微结构和宏观特性的影响是目前的研究热点,我们的研究工作包括不同种类掺杂离子、不同掺杂浓度、不同焙烧温度和不同制备方法合成的纳米二氧化锡的特性研究,特别是通过掺杂对其光学性能的改善。所得到的研究结果对于总结发光规律、吸收特性、探讨磁性机理,开辟制备新型半导体纳米材料的途径和方法,对材料科学领域基础研究及应用研究都有深远的意义。更多还原

【Abstract】 As a kind of important n type semiconduct with a wide band-gap (3.6 eV), SnO2 nano material has attracted much attention due to their terrific opto-electrical and gas sensitive properties and their potential applications in luminescent, optical absorbent, catalytic, gas sensor, DMS,and Li-ion battery cathodes materials. Doping and calcining are the best methods to be used to improve the properties of nanomaterials and expand the application area. Therefore it is meaningful for material scientific research to study the synthesis and properties of SnO2 nanomaterials doped by metallic ion.In this dissertation, the influence of doping concentration and heat treatment temperature on the microstructure, optical and magnetic properties in the transitional-metal ions Fe, Co, Mn, rare earth ion Ce, and functional ion Zn-doped SnO2 nanoparticles synthesized by sol-gel-hydrothermal method have been investigated. Based on the above experiments, we have obtained research findings as follows:1.Fe-doped SnO2 nanoparticles were synthesized by sol-gel-calcination (marked SGC-series) and sol-gel-hydrothermal (marked SGH-series) routes respectively and the optical properties were investigated for the Fe-doped SnO2 nanoparticles for the first time. The two series of samples were characterized by XRD, BET, HRTEM, FTIR, PL, DRS, MPMS.Results show that the tetragonal rutile structured SnO2 crystallites have been obtained by the hydrothermal route without calcinations and the sol-gel-calcination route. The particle size decreased with the increase of doping concentration while increased with the increase of calcinging temperature. A red-shift was observed with the increase of Fe content and calcining temperatures. At the same time, there were an UV emission (389 nm) and a blue emission (470 nm) in all samples. Paramagnetism was observed in our samples.Compared with sol-gel-calcination route, sol-gel-hydrothermal route led to better dispersed spherical Fe-doped SnO2 nanopartilces with narrower sized distribution and larger specific surface area. So the hydrothermal method was used to prepare the samples for the following research in this dissertation.2.A simple hydrothermal method has been used for the synthesis of Co-doped SnO2 nanoparticles.The optical and magnetic characteristics of the samples have been investigated by means of absorption, photoluminescence spectra and the dependence of magnetization on the temperature or magnetic field. The results shows that the crystallite size of the SnO2 samples increased with the increase of calcining temperature while decreased with the increase of Co content. A red shift was observed in SnO2 with the increase of Co content and calcining temperatures. Magnetization measurements show paramagnetic behavior in our samples.3.Influences of Mn doping concentration and calcining temperatures on the microstructure, optical and magnetic properties were investigated deeply. With the increase of Mn content, the decreasing crystalline size of SnO2 and a noticeable red shift in the UV-VIS absorption were found. The intensity of PL peak in the sample decreased after being calcined. Mn doping in SnO2 did not result in ferromagnetism based on the magnetic measurements.4. Effects of Ce doping concentration and calcining temperatures on the microstructure, optical and magnetic properties were investigated in detail.With the increase of Ce content, the decreasing crystalline size of SnO2 and a noticeable blue shift in the UV-VIS absorption were found. An UV emission and a blue emission were observed in all samples and the position of peak did not change with the increase of Ce content and calcining temperature.5.Influences of Zn doping concentration and calcining temperatures on the microstructure, optical and magnetic properties were investigated in detail.Results showed that the tetragonal rutile structured SnO2 crystallites have been obtained by the hydrothermal method when the ratio of Zn:Sn was low. With the increase of Zn content, the decreasing crystalline size of SnO2 and a noticeable blue shift in the UV-VIS absorption were found. The intensity of UV emission decreased and that of blue emission increased with the increase of Zn content. Compared with the Zn-doped SnO2 nanoparticles as-prepared, the samples after calcined showed a redshift in both absorption edge and blue emission.The influences of synthesis, doping and calcining temperature on the microstructure and properties have become a major interdisciplinary research area in recent years. My research involves the microstructure and properties of SnO2 with different metal ion dopant calcined at different temperatures and synthesized by different methods.All these results are very important for summarizing the law of luminescence and absorption, exploring the magnetism, seeking methods for the synthesis of novel semiconductive nanomaterials, and designing the new luminescent materials. We believe that it is meaningful for both basic research and application research in the material field.更多还原