Optimization Of Low Temperature Combustion Process For Fluoride Up-Conversion Luminescence Materials And Application Research

In nature,almost most of the living organisms are releasing infrared signals to the outside,and most of these infrared signals are above the middle wavelength band,and most of the current research on up conversion infrared nanomaterials is still mainly in the 980 nm band,which is mainly due to the excellent sensitization of Yb³⁺ions to the 980 nm band.However,compared with the 980 nm band,the 1550 nm band has significant advantages such as safety for human eyes,weak atmospheric absorption,and strong smoke penetration,so it has wide application prospects in laser communication,near-infrared detection,and new energy development,etc.Therefore,the study of upconversion luminescent materials with1550 nm band response is of great significance.Fluoride based rare-earth upconversion luminescent materials have the advantages of wide transmission range,easier doping of rare-earth ions into the matrix,and low phonon energy(≈500 cm^-1),so the luminescence efficiency of fluoride upconversion luminescent materials is significantly higher than that of other matrix materials.It is known that the luminescence intensity of upconversion nanomaterials will gradually increase with the increase of grain size,and when the grain size is small,the optical properties of upconversion luminescent materials are constrained by the large number of surface defects generated due to the rapid increase of specific surface area,so the requirement of achieving both fine and bright upconversion luminescent materials is an urgent problem to be solved.It is equally important to enhance the absorption of Er³⁺ions in the 1550 nm band by using a preparation process that is more beneficial to improve the intensity of the sample upconversion luminescence and by using a more superior formulation of the upconversion fluoride luminescent matrix.So this paper’s specific studies are as follows:（1）For the optimization of the preparation process of the fluoride system on the conversion of luminescent materials,the main use of solid fluoride raw materials directly involved in the combustion reaction,and through the independent introduction of oxidant and reductant raw materials to achieve the combustion reaction and combustion kinetics at a lower oxidant content,and through the study of the optical properties of the prepared samples under the action of different types of oxidant and reductant,the lower oxidant and The effects of the oxidant and reducing agent at lower oxidant and reducing agent contents were systematically analyzed and studied.（2）Specific ions were introduced into the matrix lattice of Er-Yb ion-pair inter-sensitized up conversion fluoride luminescent materials for component formulation and comprehensive performance study.The optimal doping concentration of Er³⁺ions in the Na YF₄ matrix structure and the optimal amounts of single oxidizing and reducing agents were determined using orthogonal optimization experiments with the luminescence intensity as the evaluation index,and on this basis,the energy capture center of Yb³⁺ions in the matrix structure was introduced to enhance the absorption of 1550 nm photons by Er³⁺ions using the control variable method.On the basis of the optimal concentration of Yb³⁺ions doping,Bi³⁺ions were introduced to adjust the structure of the matrix lattice to optimize the upconversion luminescence of the sample,and the effect of Bi³⁺ions introduction on the temperature sensing performance of the sample was investigated.Finally,the composition of the material with the best luminescence intensity was determined by comparison with spectroscopic tests.And based on the I-P curves of the 1550 nm excitation Er-Yb double-doped upconversion luminescent material,the role of Yb³⁺ions in the reverse energy transfer center in the Er-Yb double-doped system was clarified,and the enhancement mechanism of Yb³⁺ion doping on the 1550 nm excitation upconversion luminescent material was further investigated systematically.（3）Inert lanthanide ions were introduced into the matrix lattice of Er-Ho-Yb multi-ion synergistic inter-sensitized upconversion fluoride luminescent materials for the study of component formulation and comprehensive performance.The optimal doping concentration of Er³⁺ions was determined by the controlled variable method,and Ho³⁺ions were introduced as transient energy capture centers and mutual sensitizers for Er³⁺ions in the 1550 nm band to enhance the absorption of Er³⁺ions at 1550 nm band and the characteristic emission of Ho³⁺ions through the energy transfer between them to enhance the upconversion luminescence of the samples.The optimal doping concentration of Ho³⁺ions was determined by upconversion emission spectroscopy measurements.After the optimum doping concentration of Ho³⁺ions was determined,the utilization of 1550 nm photons by Er³⁺ions was enhanced by doping with Yb³⁺ions,and the optimum doping concentration of Yb³⁺ions was determined from the upconversion emission spectra.After that,lanthanide ions(Gd³⁺/Lu³⁺)were introduced to regulate the structure of the matrix lattice,and the optimal ion introduction concentration of Gd³⁺/Lu³⁺ions was determined by upconversion emission spectroscopy to determine the optimal component formulation for this series of samples.The I-P curves and fluorescence lifetime measurements were also used to clarify the role of the transient energy capture center of Ho³⁺ions and the passive absorption luminescence center and the reverse energy transfer center of Yb³⁺ions,and to systematically investigate the enhancement mechanism of the upconversion luminescence of the samples by the co-doping of Ho-Yb ion pairs at 1550 nm.（4）The component formulation and comprehensive performance of the Er-Tm-Yb multiple ions were investigated by introducing alkali metal ions into the matrix lattice of Er-Tm-Yb multiple ion synergistic inter-sensitized upconversion fluoride luminescent materials.The doping concentrations of Er³⁺,Tm³⁺and Yb³⁺ions were determined by the control variables method and the upconversion emission spectra,and the optimal ratio of the three ions was determined by orthogonal experiments using a three-factor four-level orthogonal table.The optimal concentration of the introduced alkali metal ions was determined by emission spectroscopy.The I-P curves and fluorescence lifetime measurements were used to clarify the role of transient energy capture center and self-absorption activation center of Tm³⁺ ions and the role of reverse energy transfer center of Yb³⁺ ions,and to systematically investigate the enhancement mechanism of Tm-Yb ion pair co-doping on the transition luminescence at 1550 nm of the sample.On the basis of this study,the effect of the introduction of alkali metal ions on the change of the crystalline phase of the matrix lattice and the effect on the transition luminescence on the sample were analyzed.（5）Based on the formulation of fluoride up conversion luminescent material components,the up-conversion display cards were prepared by screen printing process on different substrate materials,and by optimizing the preparation process and selecting the best process parameters,the problem of tight coating on different substrate surfaces by screen printing process was overcome.