The Preparation And Temperature Characteristic Research Of Two Kinds Of Luminescent Material Without Rare Earth

Luminescence materials become more and more important in our daily life. The abundant energy levels of rare earth irons make it become a hotspot. High purification cost, environmental pollution and limited resource restrict the development of rare earth materials. This article mainly studied the two types of luminescent material with no rare earth content:Carbon dot and K₂SiF₆:Mn⁴⁺. Carbon dot has has a potential application in the biological medicine, sensing, catalysis, semiconductor lighting and other fields because of its outstanding performance. The luminous mechanism is unclear and its properties need to be improved, it still need further study. As a semiconductor lighting red phosphor, K₂SiF₆:Mn⁴⁺has narrow excited range, high color purity and low cost. It's of important value to make up for the commercial color rendering of white LED. Firstly, we prepared Carbon dot and K₂SiF₆:Mn⁴⁺ red phosphors and investigated their properties at room temperature. The temperature property of the two kinds of materials was studied secondly. Finally we tried to explain the luminescence mechanism of Carbon dot and revealed the special thermal enhancement phenomenon of K₂SiF₆:Mn⁴⁺. The main research contents and conclusions are as follows:1. We studied the influence of different reaction conditions, processing methods, and additives on preparation of Carbon dot. High concentration of glucose generates excessive intermediate product, high temperature and long time generate huge amounts of carbon particles. The optimum reaction condition is under 200 ? for 1 h using O.lmol/L. Anhydrous ethanol can limit the growing up of Carbon dot, the sample has poor optical stability. Sulfuric acid can promote the synthesis of Carbon dot. More sulfuric acid content add, larger the size becomes. Carbon dot gained from ammonium oxalate hydrate has a quantum yield of 10% because of N.2. We Study the room temperature optical performance and stability of Carbon dot. The optimal excitation of Carbon dot wavelength is 350 nm, the best emission wavelength is 460 nm. The emission spectrum depends on the excitation wavelength and moves to the long wave with the excitation wavelength redshift. Carbon dot has good optical stability. Emission spectrum peak position and intensity will change with the pH value of dispersed solution,and the process is reversible and can be used for the pH sensor detection. According to the temperature characteristic of different carbon dot from glucose and ammonium oxalate hydrate, we notice the temperature quenching phenomenon, and can be used for temperature sensing. The emission spectrum under shorter excitation has faster temperature quenching speed. It verifies the quantum size effect is the main luminous mechanism of Carbon dot.3. We Studied the phase, morphology, normal temperature and variable temperature luminescence performance of K₂SiF₆:Mn⁴⁺systematically. K₂SiF₆:Mn⁴⁺ has wide absorption peak located between 400nm and 500nm, and emits red light of 600 to 650nm, and is suitable for blue white LED encapsulation. The emission peak and intensity of K₂SiF₆:Mn⁴⁺show good thermal stability. The emission peak will occur red shift with temperature rising, this is because the red shift of the zero phonon line. The color coordinates at 150 ? changes less than 0.01. Luminous intensity increase at first and decrease when temperature beyond 453K. Thermal enhancement phenomena under low temperature mainly because of the change of the quantum yield. The ratio between anti stokes emission peak and stokes emission peak intensity of K₂SiF₆:Mn⁴⁺meet good index relations with temperature, and can be used for temperature detection.