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溶液燃烧法制备的纳米晶Zn(2)SiO(4):Mn荧光粉:光谱学视角

Solution combustion derived nanocrystalline Zn(2)SiO(4):Mn phosphors: a spectroscopic view.

作者信息

Sreekanth Chakradhar R P, Nagabhushana B M, Chandrappa G T, Ramesh K P, Rao J L

机构信息

Department of Physics, Indian Institute of Science, Bangalore-560 012, India.

出版信息

J Chem Phys. 2004 Nov 22;121(20):10250-9. doi: 10.1063/1.1808420.

Abstract

Manganese doped nanocrystalline willemite powder phosphors Zn(2-x)Mn(x)SiO(4) (0.1<or=x<or=0.5) have been synthesized by a low-temperature initiated, self-propagating, gas producing solution combustion process. The phosphors have been characterized by using x-ray diffraction (XRD), energy dispersive spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and photo luminescence (PL) spectroscopic techniques. The lattice parameters calculated from XRD confirm that Zn(2-x)Mn(x)SiO(4) has a rhombohedral space group R3H. The XRD patterns confirm that Zn(2-x)Mn(x)SiO(4) phosphor samples undergo a phase transformation from beta-willemite to alpha-willemite phase at 950 degrees C. The EPR spectra of Mn(2+) ions exhibit resonance signals at g approximately = 3.24 and g approximately = 2.02, with a sextet hyperfine structure centered around g approximately = 2.02. The EPR signals of Mn(2+) give a clear indication of the presence of two different Mn(2+) sites. The magnitude of the hyperfine splitting (A) indicates that the Mn(2+) is in an ionic environment. The number of spins participating in resonance (N), the paramagnetic susceptibility (chi), and the zero-field splitting parameter (D) have been evaluated as function of x. It is interesting to observe that the variation of N with temperature obeys Boltzmann. The paramagnetic susceptibility is calculated from the EPR data at various temperatures and the Curie constant and Curie paramagnetic temperature was evaluated from the 1/chi versus T graph. The luminescence of Mn(2+) ion in Zn(2)SiO(4) shows a strong green emission peak around 520 nm from the synthesized phosphor particles under UV excitation (251 nm). The luminescence is assigned to a transition from the upper (4)T(1)-->(6)A(1) ground state. The mechanism involved in the generation of a green emission has been explained in detail. The effect of Mn content on luminescence has also been studied.

摘要

通过低温引发、自蔓延、产气溶液燃烧法合成了锰掺杂的纳米晶硅锌矿粉末荧光粉Zn(2 - x)Mn(x)SiO(4)(0.1≤x≤0.5)。采用X射线衍射(XRD)、能量色散光谱、扫描电子显微镜、傅里叶变换红外光谱(FTIR)、电子顺磁共振(EPR)和光致发光(PL)光谱技术对荧光粉进行了表征。由XRD计算得到的晶格参数证实Zn(2 - x)Mn(x)SiO(4)具有菱面体空间群R3H。XRD图谱证实Zn(2 - x)Mn(x)SiO(4)荧光粉样品在950℃时从β - 硅锌矿相转变为α - 硅锌矿相。Mn(2+)离子的EPR谱在g≈3.24和g≈2.02处呈现共振信号,在g≈2.02附近有一个六重态超精细结构。Mn(2+)的EPR信号清楚地表明存在两种不同的Mn(2+)位点。超精细分裂(A)的大小表明Mn(2+)处于离子环境中。参与共振的自旋数(N)、顺磁磁化率(χ)和零场分裂参数(D)已作为x的函数进行了评估。有趣的是,观察到N随温度的变化服从玻尔兹曼分布。根据不同温度下的EPR数据计算顺磁磁化率,并从1/χ对T的图中评估居里常数和居里顺磁温度。在紫外激发(251nm)下,合成的荧光粉颗粒中Zn(2)SiO(4)中Mn(2+)离子的发光在520nm左右显示出强烈的绿色发射峰。该发光归因于从较高的(4)T(1)-->(6)A(1)基态的跃迁。详细解释了产生绿色发射所涉及的机制。还研究了Mn含量对发光的影响。

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