Research On Properties And Application In W-LED Of Some Oxoacid Luminescent Materials Activated By Mn(4+,2+)and Eu(2+) Ions

Due to the properties of high efficiency,environmental friendly design and conservation of energy,LED was called"the fourth generation of lighting source".As the ensential component in the fabraction of the LEDs,inorganic phosphor has an important influence on the performance of the LEDs.Currently,the LEDs that possess the warm white emission are mainly utilized as the indoor lighting source.However,the most popoluar method for fabricating the w-LEDs is combining the blue and yellow emission of InGaN LED chips and the commercial YAG phosphor,respectively.The w-LEDs with this composition have a serious problem that the correalated color temperature of w-LED is high due to the insufficient red emission.If we could add a red emitting phosphor in this system exatrally,we could obtain the ideal warm white emitting LED source.Therefore,the investigation of high efficient phosphor with red emission is meaningful.Moreover,in order to avoiding the reabsorption phenomenon between different phosphors,we are aiming for the phosphors with adjustable emission wavelength.In summary,all the investigations and the adjustments are for the sake of improving the properties of w-LEDs.In this thesis,we successfully synthesized a series of phosphors according to the high-temperature solid-state method.Meanwhile,the discussions for the lattice structure,photoluminescence properties,thermal stability as well as the w-LEDs application performances are all conducted in detail.This paper mainly includes five parts as follow:(1)The SrGe4O9:Mn4+and BaGe4O9:Mn4+phosphors were successfully synthesized.The phase purity and composition were investigated by XRD,Rietveld refinement and TEM charaterizations.The luminescence properties were analysized by photoluminescence excitation and emission spectra.Acoording to the characterazations of temperature-dependent emission spectra and luminescence lifetimes,we explained the mechanisms of concentration quenching and internal thermal quenching.(2)The Mg14Ge5024:Mn4+phosphors were synthesized,and the crystallographic information of the phosphor was characterized by XRD,Rietveld refinement and TEM.The luminescence properties of the phosphor were investigated by photoluminescence excitation and emission spectra.The thermal stability and thermal quenching mechanism of the phosphor were analyzed by discussing the temperature-dependent emission spectra and the lifetimes.The applicability of the phosphor was confirmed by fabricating the w-LEDs with this red phosphor.(3)The red emission of Mg14Ge5-xAx24:Mn4+(A?Si,Ti,Sn)phosphor with high efficiency was prepared.The luminescence emission intensity and thermal stability of the phosphor were greatly improved ascribed to the REE effect and energy traps(defects)induced by cation substitution,respectively.Its unique temperature-dependent spectral property makes it possible to be applied to optical thermometry.According to a series of characterizations,the structural properties,optical properties,thermal stability and relative regulation mechanisms during the substitution process were studied systematically.(4)The(Ca,Sr)9Sc(PO4)7:Eu2+,Mn2+phosphors were successfully prepared,and the crystal field strength was controlled by cation substitution.Combining the Eu2+-Mn2+energy transfer process,1he luminescent property of the phosphor is regulated by these two effects simultaneously.Finally,a single-component phosphor system with warm white light emission is obtained.The XRD,Rietveld refinement and HRTEM were employed to characterize crystal structure evolution and nanosegregation phenomena.The mechanisms of crystal field regulation and energy transfer process were investigated by discussing the luminescence properties of phosphors.(5)The series of Sr3 Al2-xSixO5-xNxCl2:Eu2+were prepared by traditional solid-state method.The Al-O in the original phosphor system was substituted by Si-N.On the one hand,the change of crystal field strength induced by substitution could adjust the emission wavelength of Eu2+.On the other hand,the substitution causes the generation of interstitial site in the crystal structure,and the new emission peak located in the blue region emerges correspondingly.These two effects act synergistically to modulate the luminescent properties of the phosphor.The enhanced structural symmetry and rigidity improve the thermal stability of the phosphor.We conducted a detailed analysis of the structure,luminescence,thermal stability properties and performance of application in w-LED device through a series of related characterizations,and the relevant mechanisms are also discussed in detail.