Synthesis Mechanism And Luminescence Properties Of Mn(?) Activated Double Alkali Metal Ions Complex Fluoride Red Phosphors

At present,the main commercial white LED is composed of blue GaN chip and yellow fluorescent Y₃Al₅O₁₂:Ce³⁺?YAG:Ce?,which is difficult to achieve high color rendering index and low correlation color temperature due to lack of red component in the spectrum of WLED.The maximum absorption peak of the transition metal Mn⁴⁺ion doped luminescent material is located in the blue region,which matches well with the blue wavelength of the blue GaN chip,and the sharp emission peaks in the red region which can effectively improve the color rendering index of the white LED and obtain high display WLED.The raw materials of Mn are cheap and easy to obtain.The synthesis conditions are mild,the process is simple,and it is easy to scale production.Hence,we select Mn⁴⁺doped in different host lattices and explore its luminescence properties,which can provide a basis for its application in the LED field.The main research contents are as follows:Chapter 3 A novel red phosphor based on Mn⁴⁺-doped dodec-fluoride Li₃Na₃Al₂F₁₂:Mn⁴⁺with microcubic morphology was obtained at room temperature.To elucidate the underlying relationship between the crystal structure and photoluminescence of Li₃Na₃Al₂F₁₂:Mn⁴⁺,We synthesized LiNa₂AlF₆:Mn⁴⁺phosphors with similar composition and compared their micromorphology and optical properties.Compared with LiNa₂AlF₆:Mn⁴⁺,the red phosphor Li₃Na₃Al₂F₁₂:Mn⁴⁺has a blue shift in the emission peak,which indicates that the chromaticity coordinates of Li₃Na₃Al₂F₁₂:Mn⁴⁺are closer to the ideal red dot?0.67,0.33?.Moreover,the red phosphor Li₃Na₃Al₂F₁₂:Mn⁴⁺showed better luminescence properties by optimizing their synthesis conditions.After coating the red phosphor synthesized by us,a high-performance WLED with a correlated color temperature?CCT?of 3874 K and a color rendering index?CRI?of90.6 can be obtained.Chapter 4 K₂MnF₆,LiF,NaF and Ga₂O₃ are used as raw materials at room temperature,wherein LiF and NaF are higher than their stoichiometric ratio.After reacting for several hours in HF acid,the red phosphor Mn⁴⁺doped dodecafluoro Li₃Na₃Ga₂F₁₂ can be obtained.According to the experimental results,we systematically explored the formation mechanism of red phosphor Li₃Na₃Ga₂F₁₂:Mn⁴⁺and Li₃Na₃Al₂F₁₂:Mn⁴⁺.We systematically studied the optical properties of Li₃Na₃Ga₂F₁₂:Mn⁴⁺and compared it with the red phosphors Li₃GaF₆:Mn⁴⁺,Na₃GaF₆:Mn⁴⁺and Li₃Na₃Al₂F₁₂:Mn⁴⁺.According to the color coordinates of the prepared Li₃Na₃Ga₂F₁₂:Mn⁴⁺,it is observed that the red phosphor Li₃Na₃Ga₂F₁₂:Mn⁴⁺has excellent fluorescence properties and high fluorescence efficiency.When we mixed the prepared red phosphor with commercial Y₃Al₅O₁₂:Ce³⁺yellow phosphor on the GaN blue chip,it can emit warm white light which correlated color temperature?CCT?is 3986.08 K and color rendering index?CRI?is91.32.Chapter 5 We synthesized a new red phosphor LiSrGaF₆:Mn⁴⁺at room temperature,and explored its synthesis mechanism in detail.The Mn⁴⁺ion replaces the Ga³⁺ion and occupies the center of the hexahedron[GaF₆]^3-,which emits intense red light when excited by a blue or ultraviolet lamp.We also explored in detail the synthesis conditions of the reaction including the type of strontium salt,the concentration of K₂MnF₆,the concentration of NH₃·H₂O,and the temperature of the reaction.By optimizing the synthesis conditions,the fluorescence intensity of the phosphor LiSrGaF₆:Mn⁴⁺is significantly improved.The phosphor LiSrGaF₆:Mn⁴⁺synthesized by us has a wide color absorption in the blue region and a bright red light in the red region,which indicates that it has a good application prospect in warm white light WLED.Chapter 6 A novel red phosphor Li_0.5Na_1.5SiF₆:Mn⁴⁺based on the unequal dual-alkaline hexafluorosilicate with superior optical performances has been synthesized via ion-exchange between[MnF₆]^2-and[SiF₆]^2-at room temperature.The composition and the crystal structure of the as-obtained phosphor Li_0.5Na_1.5SiF₆:Mn⁴⁺were determined by EDS and XRD,respectively.Phosphor Li_0.5Na_1.5SiF₆:Mn⁴⁺has good color rendering performance and high quantum yield.Compared with the Na₂SiF₆:Mn⁴⁺and K₂SiF₆:Mn⁴⁺,the quantum efficiency of the as-obtained phosphor Li_0.5Na_1.5SiF₆:Mn⁴⁺is 96.1%.