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The Synthesize and Performance Study of Alkaline Earth Metal Vanadates Luminescent Materials R2V2O7 (R=Ca, Sr, Ba)

Author: YangKui
Tutor: MaYongQing
School: Anhui University
Course: Materials Physics and Chemistry
Keywords: Luminescence materials Alkaline earth metal Photoluminescence spectra Luminescent mechanism sol-gel method
CLC: TB34
Type: Master's thesis
Year: 2011
Downloads: 34
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Abstract


Alkaline earth metal vanadate phosphors have been attracting more and more attention in recent years because of their high luminescent intensities and stability under UV or VUV excitation as comparison with the conventional phosphors. So Alkaline earth metal vanadate phosphors have been the potential luminescent materials for light emitting diode(LED), plasma display panel (PDP), field emission displays (FED).In this dissertation, the author have studied doped (containing cation R position doped, P doped V position and rare earth doped) and undoped alkaline earth metal vanadate phosphors with molecular formula of R2V2O7(R=Ca, Sr, Ba), By means of PL, X-ray diffractometer (XRD), FTIR, SEM, we have investigated the correlation among the lattice structure, particle surface morphology and photoluminescence properties and given the reasonable explaination of the photoluminescence mechanism. Our results would be useful for the investigation and application of alkaline earth metal vanadates.The dissertation is divided into seven chapters, and the main content of each chapter is summarized as follows:In the first two chapters, we briefly introduce the preparation methods, experiment principle, characterization means and the photoluminescence properties of vanadates. V-based luminescent material can realize self-actived under certain condition, rare earth-alkaline earth metal vanadate phosphors are based on vanadium oxide host and doped rare earth ionic as activators. At present, the study on the luminescent materials of alkaline earth metal vanadates R2V2O7 as host material is still in the initial stage. It is very important to study the photoluminescence properties and the related mechanism of such materials, practically and theoretically.In chapter three, the photoluminescence properties of self-activated R2V2O7(R=Ca, Sr, Ba) are studied, which is prepared by sol-gel methord under different temperature. The experimental results show that the photoluminescence intensity of R2V2O7 (R=Ca, Sr, Ba) doesn’t depend on the variation of temperature. PL intensity of R2V2O7 (R=Sr, Ba) is very high with the broad activation band around 350 nm and the broad emission band in the region of 400-750 nm, indicating that R2V2O7 (R=Sr, Ba) may be good phosphors. However, we can’t observe the optical activity of R2V2O7 (R=Ca). We have given a reasonable explaination of the photoluminescence mechanism about self-actived R2V2O7 (R=Ca, Sr, Ba).In chapter four, the luminescent properties of R-site co-doped and V-site P doped self-activated R2V2O7(R=Ca, Sr, Ba) series of samples under UV excitation have been investigated. The R2V2-xPxO7 (R=Sr, Ba,0≤x≤0.5) phosphors show the weaker and weaker excitation and emission as x increase and R2V2-xPxO7 (R=Ca,0≤x≤0.5) doesn’t show any optical activity. So the results show that dopant P at the V-site can’t improve the luminescence performance. PL results of R1R2V2O7(Ri, R2=Ca, Sr, Ba) samples show the optical activity of 227-systems is closely related with the distance between VO43- groups, and the optical activity weakens as the distance between VO43-groups become shorter.In chapter five, we systemically study the luminescent properties of Eu3+ activated R2V2O7:Eu3+(R=Ca, Sr, Ba) under UV excitation, which is prepared by sol-gel method. The Eu3+ substitution for R2+ has changed the luminescence properties of R2V2O7:Eu3+(R=Ca, Sr, Ba) obviously. When some R-site Ca2+ ion is replaced by Eu3+, the samples take on excellent red light emission. When some R-site Ba2+ or Sr2+ ion is replaced by Eu3+, R2V2O7:Eu3+(R=Sr, Ba) take on intrinsic VO43- and Eu3+ emission at the same time. Our results indicate that R2V2O7:Eu3+(R= Ba) could be the potential white light materials.In chapter six, we study novel core shell structure SiO2@Ca2V2O7:Eu3+ phosphors. to our best knowledge, SiO2@Ca2V2O7:Eu3+is prepared for the first time by sol-gel methord. The concertration of Eu3+ is 2.5% of Ca2+. The obtained samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared microscopy (FT-IR), energy-dispersive X-ray spectra (EDS), scanning electron microscopy (SEM) and Photoluminescence spectra (PL). XRD and FT-IR analysis indicated Ca2V2O7:Eu3+ layer has formed on SiO2 surface. SEM shows clearly that the obtained core-shell phosphors have spherical shape and Ca2V2O7:Eu3+ shell is the shape of slice. PL spectra take on the characteristic emission of Eu3+(5D0→7FJ,J=1,2, 3,4), and the absoiption band of core-shell phosphors differs from that of un-coated Ca2V2O7:Eu3+ phosphor. Namely, Ca2V2O7:Eu3+ phosphor have two absorption bands located at 304 and 380 nm, but SiO2@Ca2V2O7:Eu3+ spherical particles only shows one absorption at 276 nm.Finally the brief summary and prospect of this dissertation is given in chapter seven.

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