Preparation And Luminescent Properties Of Rare Earthions Doped M₂ZnSiO₄?M=Na,K?Based Red Luminescent Materials

The rare earth ion of Eu3+or Sm3+doped M2ZnSiO4(M=Na, K) red luminescent materials were synthesized by a sol-gel method. The crystal structure, morphology and luminescent properties of samples were characterized by infrared spectroscopy, X-ray diffraction, scanning electronic microscopy and fluorescence spectrum. Influences of flux H3BO3 amount and active ion(Eu3+ Sm3+) doped amount on the fluorescence properties of the samples were studied. The concentration quenching mechanisms of activators were investigated.The Na2ZnSiO4:Eu3+ red emitting phosphors were prepared by sol-gel method. The sample obtained belongs to monoclinic crystal system and the morphology is similar to ellipsoid. The excitation spectra of the samples primarily consisted of a group of sharp peaks and the wavelength range from 350 nm to 550 nm. The main excitation peak was located at 465 nm, belonging to 7F0?5D2 typical absorbing transition. The samples transmitted a strong red light under blue light excitation with a wavelength of 465 nm. The emission bands were located at 701,653,613,591 and 578 nm, corresponding to 5 D0?7FJ(J=4,3,2,1,0) transition of Eu3+, respectively. The strongest emission peak was located at 613nm which corresponds to 5 D0?7F2 emitting transition of Eu3+. The luminescent intensity increased at first and then decreased with the increase of Eu3+mole amount. When the dosage of Eu3+ was 5% in mole, the fluorescence powder emits the most intensive luminescent intensity. Adding flux H3BO3 to sample can improve the luminescent intensity effectively and the optimal dosage of H3BO3 was 0.8% in mole.Orange-red emitting phosphors Na2ZnSiO4:Sm3+ were synthesized by sol-gel method using H3BO3 as a flux. The Na2ZnSiO4:Sm3+ phosphor obtained belongs to monoclinic crystal system and the particle size is about 2?m. The excitation spectra of the fluorescence powders consisted of a series of linear excitation peaks and the wavelength range from 330 nm to 550 nm. The emission spectra were composed of there major emission peaks using near ultraviolet with a wavelength of 404 nm as excitation light source. The emission peaks were located at 650 nm,604 nm and 566 nm, corresponding to 4G5/2?6H9/2,4G5/2?6H7/2 and 4G5/2?6H5/2 typical transition of Sm3+. The main emission peak was located at 604 nm(4G5/2?6H7/2) as reddish-orange emission. The luminescent intensity increased at first and then decreased with the increase of Sm3+ mole amount and the optimal dosage of Sm3+was 3% in mole. The concentration quenching mechanism was electric dipole-electric dipole interaction according to the Dexter theory. When H3BO3 amount is 1.5% in mole, the luminescent intensity of Na2ZnSiO4:Sm3+ phosphor reaches to the maximum, and then decreases.The K.2ZnSiO4:Eu3+ red emitting phosphors were obtained by sol-gel method using Eu3+ as an activator, the fluorescence powders synthesized belongs to orthorhombic crystal system. The sample particles are similar to regular polyhedron. The excitation spectra were composed of five excitation peaks, corresponding to f?f typical transition of Eu3+. The strongest and relatively strong excitation bands were located at 465 nm(7F0?5D2) and 393 nm(7F0?5L6), respectively. The phosphors could display red emission under a blue light or near ultraviolet source excitation. The main emission peak with a centered wavelength of 617 nm. There does not appear the concentration quenching phenomenon in the concentration ranges of the experimental measurement. Based on the X-ray diffraction patterns of the samples doped different amount of Eu3+, the impurities phase of ZnSiO3 and Zn2SiO4 can be produced when the concentration of Eu3+ is higher than the dosage of 6%. The diffraction peaks intensity of impurities phase increase with continue increasing the Eu3+ content, while the diffraction peaks intensity of the principal crystalline phase KiZnSiO4 decrease gradually, so ensuring the optimal dosage of Eu3+ was 6%.The K2ZnSiO4:Sm3+ reddish-red emitting phosphors, which can be suitable for white light-emitting diode, were prepared by sol-gel method. Based on the X-ray diffraction data, the principal crystalline phase of the fluorescence powders doped a little amount of Sm3+is K2ZnSiO4, belonging to orthorhombic crystal system. The space group of the sample is Pca21(29). The emission spectra consisted of four remarkable emission peaks under a near ultraviolet source excitation with a wavelength of 403 nm. The most intense peak was located at 605 nm, which is attributed to 4G5/2?6H7/2 transition of Sm3+. The luminescent intensity firstly increased and then decreased with increasing of the Sm3+mole amount and the optimal concentration of Sm3+was 7%. The CIE coordinates of sample locate in the reddish-orange region and do not change as increasing the mass fraction of Sm3+. The luminescent intensity of sample tend to increase in a certain concentration ranges with increasing the proportion of H3BO3. When H3BO3 amount is 4%, the phosphor exhibits the strongest luminescent intensity.