Preparation And Photoluminescence Properties Of Long-persistent Phosphorescence Doped With Lanthanides

Long-persistent phosphorescence phosphor can store the excitation energy which has been absorbed, and release it in the form of light after stop the illumination. It is a kind of photoluminescence materials. Long-persistent phosphorescence phosphors have excellent properties such as light storage, energy storage and energy saving etc. So it has important application prospect in emergency lighting, fire safety, building decoration, precise detection, biomarkers and other fields. In recent years, research on long-persistent phosphorescence has become the focus of each subject’s research.The background and research status of luminescent material have been summarized and generalized by this paper. The the preparation and luminescence properties of several new different colors long-persistent phosphorescence have also been researched in this paper. This paper is divided into six chaptersThe first chapter expounds the basic concept of long-persistent phosphorescence materials, this paper introduces the development history and research status quo of long-persistent phosphorescence materials, summarizes the advantages and disadvantages of all kinds of long-persistent phosphorescence materials, and makes a brief introduction of t the preparation methods, characterization means and growing history of long-persistent phosphorescence phosphors.In Chapter 2, a series of Na2CaSn2Ge3O12:Sm3+ long-persistent phosphorescence phosphors were prepared by conventional high temperature solid-state method. XRD analysis shows that all samples contain Na2CaSn2Ge3O12 as predominant phase. Under 255 nm UV excitation, the photoluminescence spectrum of samples is made up of a series of double splitting peaks which are located at 566 nm,605 nm,664 nm and 724 nm, the concentration quenching value of Sm+ is 1 mol%. The afterglow decay curve of all samples can fitting with the second exponential equation. By analyzing the thermoluminescence data, it is found that the incorporation of Sm3+ not only increases the trap types, but also greatly increases the concentration of various traps, which leads to afterglow time of Na2CaSn2Ge3O12:1.0% Sm3+ sample is longer than 4.8 h. The mechanism of the generation of long afterglow phenomena is discussed in detail.In Chapter 3, the Na2CaSn2Ge3O12:Eu3+ and Na2CaSn2Ge3O12:Eu3+,Dy3+ reddish orange long-persistent phosphorescence phosphors were synthesized by high temperature solid-state method. XRD analysis shows that the main phase of all samples is Na2CaSn2Ge3O12. Under 318 nm UV excitation, the photoluminescence spectrum of all samples is composed of the characteristics emission peak of the Eu3+(triple split peak of 5D0-7F1 transition), the site which was occupied by Eu3+ possess inversion symmetry. The optimal doping concentration of Eu3+, Dy3+ is 1.2 mol% and 0.4 mol% respectively. The results of afterglow decay indicate that the afterglow decay curves of all the samples can be fit with second exponential equation. Although co-doping Dy3+ in Na2CaSn2Ge3O12:Eu3+ reducing the emission intensity of the sample, but increase its afterglow time from 15 min to 5 h. Thermoluminescence studies reveal that the incorporation of Dy3+ significantly increased the concentration of original trap, therefore improves the ability of trap capture and release carrier, this ultimately results in the emission peak intensity of the sample which was co-doped with Dy3+ decreases, and afterglow time of it is greatly increased. The mechanism of this phenomenon is discussed in detail.In Chapter 4, prepare a series of Na2CaSn2Ge3O12:Dy3+ long-persistent phosphorescence phosphors using high temperature solid-state method. The influence of Dy3+ doping concentration on the samples properties was discussed by the study of the XRD, the photoluminescence excitation and photoluminescence spectra, afterglow decay curves and thermoluminescence curves of these samples. The results reveal that the predominant phase of all the samples is Na2CaSn2Ge3O12. Under 248 nm UV excitation, all the samples are emit yellowish-white light which is composed of blue and yellow light, which are caused by 4F9/2-6H/J=(15/2,13/2,11/2) characteristics transition of Dy3+. It can be seen from afterglow decay curve of the samples that this process involves a rapid decay process and then a slow decay process. The sample has the strongest emission intensity and longest afterglow time when the doping concentration of Dy3+ is 0.6 mol%, and the afterglow time of it is more than 7.8 h. The CIE of the Na2Ca0.994Sn2Ge3O12:0.6% Dy3+ is (0.3963,0.392). Thermoluminescence data analysis indicated that the incorporation of Dy3+ can increase both the trap types and concentrations of the traps in the samples. Finally the mechanism of long afterglow is discussed in detail.In Chapter 5, synthesis a series of Pr3+-doped Na2CaSn2Ge3O12 Long persistent phosphorescence phosphors using high temperature solid-state method. The XRD, photoluminescence excitation (PLE) and emission (PL) spectra, afterglow decay curves and thermoluminescence (TL) curves were measured to systematically investigate the properties of Na2CaSn2Ge3O12:Pr3+ samples. From XRD date, it can be seen that a predominant phase of Na2CaSn2Ge3O12 was formed in all samples. Under 256 nm UV light excitation, all samples emit the characteristic emission of Pr3+ due to the 3P0-3H4 and 1Da2-3H4 transition. It is also observed that the emission intensity of Na2CaSn2Ge3O12:Pr3+ sample is strongest when the concentration of Pr3+ is 0.8%, and the afterglow time is 3 h. The afterglow decay curves revealed that the afterglow decay of all samples was the second exponential decay. Through analysis of thermoluminescence curves, it can be seen that doping Pr3+ into Na2CaSn2Ge3O12 matrix not only can increase the types of traps in the samples, but also increased the concentration of the trap. The afterglow luminescence mechanism of these samples was discussed in detail finally.