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Grandhe, Bhaskar Kumar,Bandi, Vengala Rao,Jang, Kiwan,Ramaprabhu, S.,Lee, Ho-Sueb,Shin, Dong-Soo,Yi, Soung-Soo,Jeong, Jung-Hyun Elsevier 2012 Composites. Part B, Engineering Vol.43 No.3
<P><B>Abstract</B></P> <P>YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites have been synthesized by means of a modified co-precipitation method (CP-CNT). Multi walled carbon nanotubes (MWCNT’s) have been employed in the synthesis of the YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites to enhance its photoluminescence efficiency. The prepared nanocomposites were thoroughly characterized using the characterization techniques namely XRD, SEM, FTIR and Raman scattering. To evaluate the potentiality of the prepared nanocomposites, the same phosphor has also been prepared by using co-precipitation (CP) method without employing multi walled carbon nanotubes and also by means of conventional solid state reaction method (SSR). The photoluminescence spectra of YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites have shown stronger red emission at 619nm (<SUP>5</SUP>D<SUB>0</SUB> → <SUP>7</SUP>F<SUB>2</SUB>) for both the excitation wavelengths (254 and 393nm) than the other two prepared samples. The effect of MWCNT’s on photoluminescent properties of the YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites is also explained.</P>
Bhaskar Kumar Grandhe,Vengala Rao Bandi,장기완,김상수,신동수,이용일,임재민,송태권 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.3
Eu3+ doped Gd2O3 nanotubes have been synthesized using multi wall carbon nanotubes as removable templates by employing a liquid phase deposition method. The prepared Eu3+ doped Gd2O3 nanotubes were characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy, fourier transform infrared sepctroscopy and thermogravimetry and differential thermal analysis. XRD patterns conrm the cubic phase of Eu3+ doped Gd2O3 nanotubes. From the measured SEM images,the average diameter of the Eu3+: Gd2O3 nanotubes were estimated to be in the range of 50-70 nm. The photoluminescence analysis revealed that the Eu3+: Gd2O3 nanotubes can display a strong red emission peak at around 616 nm, due to the 5D0→7F2 electric dipole transition of Eu3+ ions. Such luminescent powders are expected to find potential applications in fluorescent lamps and display device applications.
Enhanced Red Emission from YVO_4:Eu^(3+) Nano Phosphors Prepared by Simple Co-precipitation Method
Bhaskar Kumar Grandhe,Vengala Rao Bandi,Kiwan Jang,Sundara Ramaprabhu,이성수,Jung-Hyun Jeong 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.2
Eu^(3+) doped YVO4 nano phosphors were synthesized by adopting a simple Co-Precipitation Method (CPM). In order to compare and evaluate this method’s potentiality, we prepared the same phosphor by using a conventional Solid State Reaction method (SSR). X-Ray Diffraction (XRD) profile confirms the tetragonal nature of Eu^(3+) doped YVO4 nano phosphors. The efficiency of the prepared phosphors was analyzed by means of its emission spectral profiles. We also observed a rich red emission from the prepared phosphors under a Ultra-Violet (UV) source. Such luminescent powders are expected to be applied as red phosphors in display device applications. In addition, Scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier-Transform IR spectroscopy (FTIR), and Raman Spectrum were also used to characterize the synthesized phosphor.
Dillip, G.R.,Kumar, Grandhe Bhaskar,Bandi, Vengala Rao,Hareesh, M.,Deva Prasad Raju, B.,Joo, S.W.,Bharat, L. Krishna,Yu, Jae Su ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.699 No.-
<P><B>Abstract</B></P> <P>A single-phase white-light-emitting phosphor, K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP>, has been synthesized by a conventional solid-state reaction method. X-ray diffraction (XRD) analysis was used to determine the monoclinic crystal structure of phosphors. The surface states, B 1s, O 1s, K 2p, Zn 2p, and Dy 3d of the phosphor was quantified by X-ray photoelectron spectroscopy (XPS). Diffuse reflectance spectroscopy (DRS) revealed double absorption edges at 3.27 and 5.46 eV for K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB> matrix. The formation of defect-levels, zinc interstitials ( Z <SUB> n i </SUB> ) , zinc vacancies ( <SUB> V Z n </SUB> ) , oxygen antisites ( <SUB> O Z n </SUB> ) and oxygen vacancies ( <SUB> V O </SUB> ) in K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP> phosphors were identified by photoluminescent (PL) spectroscopy. The emissions at 405 nm (violet-I), 434 nm (violet-II), and 467 nm (blue) are due to intra-band transitions of ( F X → <SUB> V Z n </SUB> ) , ( Z <SUB> n i </SUB> → <SUB> V Z n </SUB> ) and ( Z <SUB> n i </SUB> → <SUB> O Z n </SUB> ) of the host, respectively. Similarly, the emission at 517 nm (green) corresponds to the transition from free excitons to the oxygen vacancies in the host ( F X → <SUB> V O </SUB> ) . The emissions at 575 and 665 nm are assigned to the <I>f-f</I> transitions of Dy<SUP>3+</SUP> ions within the host matrix. An energy level diagram is proposed to describe the host emission and possible energy transfer from the host to dopant ions in the single-phase phosphor. The phosphor shows good thermal stability with activation energy of 0.52 eV. The combined emissions in the blue, green, yellow, and red regions resulted in white light emission with CIE coordinates of (0.256, 0.258) on the CIE diagram.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Versatile host-sensitized white light emission, K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP> phosphor was synthesized. </LI> <LI> Defect-related surface analysis of phosphor was studied by XPS. </LI> <LI> Energy level diagram was designed to show host to dopant energy transfer process. </LI> <LI> The phosphor has shown good thermal stability with activation energy of 0.52 eV. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
정준호,이호섭,Vengala Rao Bandi,Bhaskar Kumar Grandhe,장기완,이성수,정중현 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2
Eu^(3+) or Sm^(3+) singly-doped and Eu^(3+) and Sm^(3+) co-doped KZnGd(PO_4)_2 phosphors were synthesized by using a conventional solid state reaction method at 750 ℃. The emission spectra of KZnGd_(1−x)(PO_4)_2:Eu_^(3+)_x with λ_(ex) = 395 nm and KZnGd_(1−y)(PO_4)_2:Sm^(3+)_y with λ_(ex) = 403 nm phosphors showed intense ^5D_0 → ^7F_1, ^4G_(5/2) → ^6H_(7/2) emission transitions at 595 nm and 599 nm, respectively. The optimum relative intensity of the KZnGd_(1−x−y)(PO_4)_2:Eu^(3+)_xSm^(3+)_y phosphor was obtained for the doping concentrations of (x = 0.09, y = 0.01). In addition, the temperaturedependent luminescence intensity of the synthesized phosphors was investigated and the thermal stability of the KZnGd(PO_4)_2:Eu^(3+) phosphor was found to be higher than that of standard YAG:Ce^(3+) and KZnGd_(1−x−y)(PO_4)_2:Eu^(3+)_xSm^(3+)_y under near ultra-violet (NUV) light emitting diode excitation (LED). Therefore, we suggest that Eu^(3+) or Sm^(3+) singly-doped and Eu^(3+) and Sm^(3+) co-doped KZnGd(PO_4)_2 phosphors should be efficient for different red-color-emitting display device applications and NUV-LED-based white-light-emitting diodes.
Woo, Hyun-Joo,Bandi, Vengala Rao,Grandhe, Bhaskar Kumar,Jang, Kiwan,Park, Jiyeon,Yoon, Jaeho,Lee, Ho-Seub,Bae, Dong Hyun,Yi, Soung-Soo,Jeong, Jung-Hyun American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.2
<P>A novel phosphor namely CaLa2ZnO5 doped with Eu3+ ions were prepared by conventional solid state reaction method. We have studied and optimized various constraints like sintering temperature, sintering time and dopant concentration. XRD, SEM profiles have been studied to explore its structural properties. Luminescence properties of these phosphors have been characterized by means of their photoluminescence (PL) spectra. We have noticed that the emission intensity of CaLa2ZnO5:Eu3+ phosphors strongly depend on its sintering temperature and Eu3+ concentration. Moreover, their PL spectra reveals that CaLa2ZnO5:Eu3+ phosphors exhibits a strong luminescence of 5D(0)_7F(2) transition at 627 nm under the excitation of 468 nm, which correspond to the popular emission line from a GaN based blue light-emitting diode (LED) chip. The obtained results of the prepared Eu3+ doped phosphors are very much encouraging and they are potentially useful in the development of new solid-state lightning devices.</P>