Light-emitting diodes (LED) as a new generation of lighting source has the advantages of small volume、long life and low calorific value,has been widely used in display, lighting, automotive industry and other fields.Because of its narrow emission spectrum and unique wavelength advantage, it is also considered as an effective alternative light source for indoor plant lighting.As an important part of LED, phosphors can produce monochromatic light with rich colors such as red,green and blue according to different host types and doping ions.However,the research on far-red emitting phosphors needed plant lighting still needs to be further improved.As a transition ion,Mn4+has an unfilled 3d3 electron configuration and a wide absorption band (250 - 550 nm).When Mn4+is located in the octahedral lattice,red emissions at 620-800 nm are observed due to the 2E→4A2 transition,which is matched with the absorption wavelength of phytochromes.Therefore,the application of Mn4+ ions in the field of plant lighting has attracted extensive attention of researchers.At present,in the process of preparing white light-emitting diode (WLED), the problems such as color reabsorption and low color rendering index need to be solved urgently.Therefore,it is of great significance to develop new single-phase phosphors.The luminescence properties of doped Mn4+,Bi3+and Sm3+in LaSrZnNbO6 host and the mechanism of energy transfer between Bi3+and Sm3+were investigated, the main research contents are as follows:(1)For LaSrZnNbO6:Mn4+,there are two excitation bands in the excitation spectra measured at 694 nm.The absorption band centered at 320 nm is attributed to the charge transfer transition from O2-→Mn4+,while the absorption band centered at 366 nm is credited to the 4A2→4T1 transition of Mn4+.The weak absorption bands centered at 432 nm and 505 nm are due to the 4A2→2T2 and 4A2→4T2 transitions of Mn4+, respectively.The emission peak appeared at 694 nm,which is matched well with the absorption wavelength of phytochromes,is caused by the 2E→4A2 transition of Mn4+ions.With increasing the Mn4+ion concentration,the decay times of LaSrZnNbO6:Mn4+are decreased from 0.2694 to 0.2448 ms.The chromaticity coordinate is (0.7199,0.2801),which is the far-red emission.In order to improve the emission intensity of LaSrZnNbO6:Mn4+phosphor,boric acid was also introduced as a flux in this experiment and explore its influence on the luminescence intensity of the sample.The phosphor is conducive to plant growth and has potential applications in the field of plant lighting.(2)According to the excitation and emission spectra,it can be seen that the maximum excitation position of LaSrZnNbO6:Bi3+phosphor is 338 nm,which belongs to the absorption of 1S0→3P1 of Bi3+.Under the excitation condition of 338 nm,the blue emission of the sample is the strongest at 432 nm and the optimal doping concentration is 9 mol%.When LaSrZnNbO6:Sm3+phosphors are excited by 406 nm near-ultraviolet light, the maximum emission peak is located at 601 nm,and the sample appears orange-red emission.The emission spectra of Bi3+and Sm3+co-doped LaSrZnNbO6 phosphors exhibit both of Bi3+and Sm3+emission peaks with excited at the excitation wavelength of Bi3+(338 nm).It indicates that Bi3+→Sm3+energy transfer exists in LaSrZnNbO6 host.By calculating, the energy transfer efficiency between Bi3+and Sm3+ions can reach 86.9%.The CIE coordinates of LaSrZnNbO6 phosphor can be moved from the blue region to the pink-white region by changing the doping concentration of Bi3+and Sm3+ions,indicating that colortunable phosphor can be prepared by adjusting the doping concentration. |