Synthesis And Optimization Of Red-emitting Nitride Phosphors With High Performance

Nowadays,the environmental pollution and the excessive energy consumption have already affected the people's daily life.So,the energy conservation and environmental protection has become one of the hot topics in this era,and more attention has been paid to the development of energy-saving and environment-protecting technologies.The development of white Light Emitting Diode?LED?met both requirements in the illumination and display fields.The white LEDs have become one of the most popular devices replacing traditional lighting equipment,due to their long life,low pollution,low energy consumption and high display performance.The most traditional way to obtain white LEDs is to combine the blue LED chips with the Y3Al5O12:Ce3+ yellow phosphors.The method has been widely used since its discovery for more than twenty years.But with the improvement of people's quality of life,the requirements for luminous device are further improved.The white light based on the traditional method could not meet the requirement of daily use,due to its lack of the red part.In order to get a better white LED,the red-emitting phosphor is absolutely necessary to make up for the lack of red light.And the red-emitting phosphor should be excited by blue light,because the most widely used LED chips are blue-emitting.Now,the most widely used red-emitting phosphors are Sr₂Si₅N₈:Eu²⁺ and CaAlSiN3:Eu²⁺ nitride phosphors.So,the detailed study on nitride phosphors is very necessary.In contrast to other phosphors,the red-emitting phosphors have low emission intensity and quantum efficiency.Therefore,it is very helpful for commercial application to get the higher performance of red-emitting nitride phosphor.There are many ways to improve the performance of phosphor,such as looking for new host or doped ions,emission enhancement by surface plasmon,increasing the stability,and so on.Due to the above reasons,this paper will study the synthesis and optimization of high performance red-emitting nitride phosphors and be divided into seven chapters.Chapter 1 is the introduction,which mainly introduces the light,luminescence,and the development of LEDs.Meanwhile,the classification and synthesis methods of phosphors are introduced.In addition,two kinds of high performance red-emitting phosphors mentioned in this paper are also introduced.Chapter 2 is the experimental part.It introduces the experimental materials,devices and application methods,and ensure the unity of the whole experiment.Chapter 3 and Chapter 4 mainly introduce the enhancement of the emission intensity of the commercial Sr₂Si₅Ns:Eu²⁺ phosphor.Chapter 3 mainly introduces the synthesis method of silver nanoparticles and the effects of different synthesis conditions on the morphologies of silver nanoparticles.The silver nanoparticles suitable for enhancing the luminescence properties of Sr₂Si₅N₈:Eu²⁺ phosphor were successfully synthesized.In chapter 4,the commercial Sr₂Si₅N₈:Eu²⁺ phosphor powder was enhanced by silver nanoparticles.The results showed that when the absorption spectra of silver nanoparticles were overlapped with the excitation or emission spectra of Sr2Si5Ns:Eu²⁺ phosphor,the emission intensity could both be enhanced,but the enhancement effect was different.When silver nano-rods and silver nano-spheres were mixed in a certain proportion,the maximum enhancement of about 25%could be achieved.It is significant for improving the commercial phosphors.In chapter 5,the synthesis of Sr[LiAl₃N₄1:Eu²⁺ phosphors was studied.The target phosphor was successfully synthesized by high temperature solid reaction method,and the carbon thermal reduction method was not suitable for the phosphor.In addition,through a lot of doping experiments on Sr[LiAl₃N₄]:Eu²⁺ phosphor,the influence of various ions in the phosphors was preliminarily explored.Most of these ions directly act as fluorescence quenching agents,causing the decrease of the emission intensity.But a small amount doping of Si could slightly enhance the emission intensity.These results provide an important basis for the development of Sr[LiAl₃N₄]:Eu²⁺ phosphor.Chapter 6 uses PDMS as the raw materials to modify the phosphor,because the Sr[LiAl₃N₄]:Eu²⁺ phosphor is easy to react with water.After modification,the phosphor was successfully transformed into hydrophobicity with a contact angle of more than 140°.Compared with the unmodified samples,the modified samples could maintain high luminescence performance for longer time under extreme environments,and the time is more than twice that of the unmodified samples.Chapter 7 is a summary of the full text,and introduces the deficiencies in this paper as well as the part that can still be discussed in the future...