Preparation And Luminescence Properties Of Phosphors BaY₂S₄ For LED

White light emitting diodes (LED) have attracted widespread interest due to their attractive attributes such as little volume, long lifetime, high efficiency, energy-saving, environment friendly and so on, it is considered to be the fourth generation light source following the incandescent, fluorescent, high intensity discharge lamps. There are many approaches to achieve white LED, the most mature method for achieving white LED is phosphor conversion. Therefore, more and more research has been paid to the preparation and the spectral properties phosphor for white LED.Rare-earth ternary sulfides with the formula MRE2S4 (M=Ca, Sr, Ba; RE=La, Y) have bandgaps in the range of 2.3-3.6 eV so that the materials appear to be suitable phosphor hosts. In addition, MRE2S4 have the excellent thermal stability, strength and infrared transmission characteristics, make themselves good candidates to be studied for novel IR optical window materials. So, there are significance theoretics and application value for the study of rare earth ions doping MRE2S4.The trivalent holmium ion (Ho3+) is well known as having rich energy levels in the visible, an appropriate selection of the host lattice is possible to yield simultaneously multi-bands emission in the visible. BaY2S4:Ho3+phosphor was prepared in this article, it is found that the phosphor simultaneously emit red, green and blue-green three band spectrum under the blue light excitation, adjusting the ratio intensity of each emission peak, then it can available the phosphor for white LED with blue light excitation. To improving the luminescence properties of phosphors, in this paper, we studied the holmium ion activated BaY2S4 phosphors on basis of sensitized luminescence and solid solution matrix.1. Preparation and luminescence properties of novel phosphor BaY2S4:Ho3+The starting materials was BaCO3, Y2O3, Ho2O3 and HNO3, and CS2 was used as sulfuration agent, the phosphors were synthesized directly by the high temperature solid-state reaction and its luminescent properties was researched. Under 465 nm light excited, the emission spectra of the phosphors shows three major emission peaks locating at 492 nm,543 nm and 661 nm corresponding to the 5F3â†'5I8, (5S2,5F4)â†'5I8 and 5F5â†'5I8 typical transitions of Ho3+, respectively. With the concentration of holmium doping changes, the ratio of emission intensity of the phosphors in the blue-green region, green region and red region can be controlled. The results shows that select the appropriate concentration of Ho3+, it can get a yellow phosphor excited by blue light.2. The influence of rare earth ions on the spectral properties of phosphors BaY2S4:Ho3+A series of rare earth were introduced in to the phosphor BaY2S4:Ho3+, the luminescent properties of the BaY2S4:Ho3+,RE phosphors with different variety and doing content were studied and compared. The results shows that rare earth ions in the BaY2S4:Ho+ phosphor have not enhanced the emission intensity of the phosphor. Co-doped RE ions can be closer to the ratio of the red emission intensity and the green emission intensity by competition or non-radiative transition among levels.3. Influence of solid solution on the luminescent properties of phosphors Ba(Y1-yAly)2S4:Ho3+ Ba(Y1-yAly)2S4:Ho3+phosphors were synthesized by high temperature solid-state reaction. The XRD results indicated that the power samples was pure phase of BaY2S4 when the doping content of Al3+ions in the matrix Ba(Y1-yAly)2S4:Ho3+was less than 30 mol%, but there appeared impurities BaAl2S4 when the Al3+-doping concentration was more than 30 mol%. Emission intensity of Ba(Y1-yAly)2S4:Ho3+ phosphors depends strongly on the Al3+concentration, with the increasing Al3+doped content (y), the emission peak position of Ba(Y1-yAly)2S4:Ho3+ did not move, but its emission intensity first increases and then decreases, The emission intensity of Ba(Y1-yAly)2S4:Ho3+reached maximum when y is equal to 0.3, compared with that of undoped Al3+ion, its emission intensity increased by 2.5 times. Due to the good thermal stability and not easy deliquescence, Ba(Y1-yAly)2S4:Ho3+was considered as a potential applied singly-phase yellow phosphor for white LED.4. Synthesis and luminescence properties of phosphor BaY2S4:Eu2+,Tb3+BaY2S4:Eu2+,Tb3+phosphors were synthesized, Fluorescence analysis showed that the emission spectra of the phosphor contained a broadband covering 470 nm-650 nm. In BaY2S4:Eu2+,Tb3+phosphor system, there occurred energy transfer from Eu2+to Tb3+ion.