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Structural and spectroscopic diagnosis of ZnO/SnO_2 nanocomposite influenced by Eu^(3+)

Journal of Rare Earths 2015年第8期33卷 805-813页

作者： pankaj kr.baitha J.Manam Department of Applied Physics Indian School of Mines

Europium doped ZnO/SnO2 nanocomposite phosphors were synthesized via room temperature co-precipitation method. In this work structural changes, optical properties and the associated photoluminescence response were investigated for different compositions of ZnO and SnO2 activated with Eu3＋ ions. The prepared samples were systematically characterized by means of X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, field emission scanning electron microscopy for obtaining the structural information about the prepared materials. Diffuse reflectance （DR） UV-Vis spectrometer and photoluminescence （PL） spectroscopy technique were employed for studying the optical properties of prepared materials. XRD results confirmed the presence of both phases, hexagonal ZnO as well as tetragonal SnO2 simultaneously and further using Debye Scherrer＇s and Hall-Williamson relations, crystallite size were estimated and it was found to be in the range of 8-14 nm. The FTIR studies revealed the presence of different stretching and bending modes of Zn-O and Sn-O with an additional stretching and bending vibration of absorbed water （O-H） molecules. FESEM images suggested that the particle size lied in the range of 50 to 70 nm, which were almost spherical in shapes. A long range multi colour emission from blue to red region was observed for the 320 nm excitation wavelength. The observed emission involved sharp emission due to 5D0→7F1 transition that corresponded to the magnetic dipole transition. The study showed that the Eu3＋ doped nanocomposite was more suitable material than singly Eu3＋ doped ZnO and Eu3＋ doped SnO2 with enhanced opto-eleetronic and luminescence properties and potential applications in display devices.

关键词： ZnO/SnO2 nanocomposite europium doping photoluminescence co-precipitation rare earths

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Influence of heat treatment on the structural and optical properties of SrGd_2O_4:Eu^(3+) phosphor

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Journal of Rare Earths 2015年第10期33卷 1040-1050页

作者： Jyoti Singh pankaj kr.baitha J.Manam Department of Applied Physics Indian School of Mines

Novel red emitting Eu3＋ doped SrGd2O4 phosphors were synthesized by homogeneous precipitation method followed by a subsequent combustion process at various temperatures. A systematic study on the consequent structural evolution and optical properties were investigated as a function of various processing temperatures. With the enhancement of processing temperature, SrGd2O4 phosphor showed a gradual transformation from a mixed phase to monophasic nature, with minimized volatile imptwities. The microscopic images exhibited homogeneous aggregates of varying shapes and sizes with an average length of about 0.5-5μl. Eu3＋ doped SrGd2O4 phosphors prepared at low temperatures, showed miserably low values of red emission upon UV excitation owing to the presence of volatile impurities. The SrGd2O4：Eu3＋ phosphors prepared at relatively high temperature exhibited strong red-orange emissions due to homogeneously occupied Eu3＋ ions in the host lattice. The dominant red to orange （R/O） emission intensity ratios and CIE parameters of EU3＋ ions substantiated the site occupation of higher asymmetry sites of Gd3＋ ions and the strong covalent nature. Dexter theory and critical distance calculation suggested that the dipole-dipole interaction could be responsible for the concentration quenching of Eu3＋（4 mol.%） doped SrGd2O4 phosphors. Elevated physical and chemical durability and stable photoluminescence made these phosphors suitable for white LEDs and other display applications.

关键词： optical materials chemical synthesis X-ray diffraction luminescence rare earths

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印度黑颈鹤现状与分布

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Zoological Research 2014年第S1期35卷 39-50页

作者： pankaj Chandan Afifullah Khan Jigmet Takpa Syed A.Hussain Kamal Mehdi Pushpinder Singh Jamwal Rohit Rattan Nisa Khatoon Tsewang Rigzin Anupam Anand Pijush kr.Dutta Tanveer Ahmad Partha S.Ghose Priyadarshinee Shrestha Lak Tsheden Theengh WWF-India 172-BLodi EstateNew DelhiIndia Aligarh Muslim University AligarhIndia Department of Wildlife Protection Ladakh J&KGovernmentIndia Wildlife Institute of India DehradunGovernment of IndiaIndia University of Maryland USA Tata Institute of Social Sciences Guwahati CampusIndia

为了弄清和监测印度黑颈鹤(Grus nigricollis)的现状与分布,作者于2000-2014年开展了长期研究。每年在所有已知的黑颈鹤分布点开展调查,同时探索了新的区域。基于黑颈鹤的历史分布区,包括查谟和克什米尔、锡金等的文献记载和调查,该文... 详细信息

为了弄清和监测印度黑颈鹤(Grus nigricollis)的现状与分布,作者于2000-2014年开展了长期研究。每年在所有已知的黑颈鹤分布点开展调查,同时探索了新的区域。基于黑颈鹤的历史分布区,包括查谟和克什米尔、锡金等的文献记载和调查,该文对印度黑颈鹤的现状与分布进行了综述,详细列出了黑颈鹤在印度的当前现状与分布。首次对过去15年来印度黑颈鹤种群状况进行了报道:整个研究期间,于2012年在拉达克的繁殖地最多记录到139只黑颈鹤个体,于2006年在印度东北部记录到11个越冬个体。

关键词：黑颈鹤高海拔湿地拉达克锡金

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