| The rare earth and transition metal ions doped luminescent materials,as one of the most common solid-state luminescent materials,have been extensively used in optical anti-counterfeiting,biomedicine,solid-state lighting,sensing and laser fields.In fact,the application direction of solid-doped luminescent materials often depends on their own luminescent properties.For example,in the field of optical temperature measurement,the temperature sensing is often achieved by using the optical characteristics which are strongly dependent on temperature,while in the application of phosphor,the high quenching temperature of luminescent materials are required.Therefore,to meet the application requirements in different fields,the luminescent properties of luminescent materials need to be studied in detail.In our research work,we mainly explore the application prospect of luminescent materials in non-contact temperature sensing,and as near-infrared phosphors.Therefore,in this thesis,we mainly carried out a series of studies on the preparation and spectral analysis of luminescent materials,among which we focused on the luminescent temperature properties of the synthesized materials,so as to provide a powerful basis for exploring their application in optical temperature sensing and as near-infrared phosphors.The specific research system covers inorganic luminescent materials activated by Tb3+,Cr3+and Mn4+,and the main contents and results are shown as follows:In the first chapter,we first introduce the significance of researching non-contact optical temperature sensor and developing high-efficiency near-infrared phosphor,then we introduce the definition,classification and characterization of luminescence,subsequently,the reasons of Stokes shift and fluorescence temperature quenching are explained by means of the configuration coordinate model theory,at last,the luminescent properties of rare earth and transition metal ions,as well as the commonly used optical temperature detection techniques are introduced in detail.In the second chapter,the temperature property of Ba2LaF7:Tb3+transparent glass ceramics and its application in temperature sensing are studied.In this material system,we chose to use the thermally coupled energy levels of the ground and low-lying excited states of Tb3+ions(7F6 and 7F5)for temperature sensing.Using this scheme,the biggest advantage is that it can effectively avoid the decoupling of the two energy levels at low temperature.The number of Tb3+ions at the 7F5 energy level increases with the increase of temperature.Therefore,under a specific excitation of 7F5→5D4,the emission intensity of Tb3+ions will be also enhanced as the temperature rising.The experimental results show that the emission intensity of 5D4→7F6 increases rapidly in the studied temperature range(300-630 K)with the increase of temperature when excited at a specific wavelength of 543 nm.The relative sensitivity based on this method reaches 2.88%K-1 at 300 K.In the third chapter,the dual-mode temperature sensing based on the mixture phosphor of LiAl5O8:Cr3+and LuPO4:Tb3+is studied.To overcome the restriction of thermal coupling condition to improve the relative sensitivity,a temperature measurement scheme based on the fluorescence intensity ratio of non-thermally coupled energy levels of two luminescent centers is proposed.Under a specific excitation of Tb3+(7F5→2D4),the emission intensity of Tb3+and Cr3+in the mixture shows opposite temperature dependence.The experimental results show that the temperature measurement scheme based on the fluorescence intensity ratio of Tb3+(5D4→7F4)and Cr3+(2E→4A2)further improves the relative sensitivity of temperature sensing,and its value can reach 3.68%K-1 at 300 K.In addition,the temperature-sensitive lifetime of Cr3+ in the mixture phosphor can also be used for temperature sensing.Therefore,the mixture phosphor of LiAl5O8:Cr3+and LuPO4:Tb3+is one of the promising candidates for the construction of dual-mode high sensitivity temperature sensors.In the fourth chapter,the potential of time-resolved measurement based on the fluorescence of InTaO4:Cr3+ for temperature field imaging is studied.Nowadays,in the field of micro/nano electronics,the resistive heating effect caused by the reduction of the size of electron conduction channel has a great influence on the performance of electronic components,such as shorten the service life of the device or direct damage to the device.Therefore,the temperature detection in this field not only needs to meet the requirements of high precision and non-contact measurement,but also needs the ability to reproduce the entire surface temperature distribution of electronic components,in order to find the heating area that affects the performance of the device in time.In this work,the InTaO4:Cr3+phosphor was prepared by classic solid phase method.Under the excitation of 500 nm,the InTaO4:Cr3+samples with doping concentration of 1%～4%present the optimal luminescence.The temperature-dependent emission spectra and fluorescence decay curve of In0.96TaO4:0.04 Cr3+ sample were measured over a temperature range of 240-420 K.Due to the characteristic that the fluorescence lifetime of Cr3+ decreases rapidly with the temperature increasing,another novel temperature measurement scheme based on the time-resolved spectroscopy measurement of Cr3+is proposed.The results show that the relative sensitivity is greatly improved by using this temperature measurement scheme,whose value reaches a maximum of 5.03%K-1 at 388 K.By combining fluorescence microscope and ICCD detector,.the scheme has been successfully applied to the temperature imaging on a printed circuit board,realizing the monitoring of the surface temperature distribution of the microcircuit.In the fifth chapter,the potential of time-resolved measurement based on the fluorescence of Li2TiO3:Mn4+for temperature field imaging is studied.Compared to the material system of InTaO4:Cr3+,the fluorescence intensity and fluorescence lifetime of Li2TiO3:Mn4+sample are more sensitive to temperature.Therefore,the temperature measurement scheme based on the time-resolved spectroscopy measurement of Li2TiO3:Mn4+further improves the relative sensitivity of temperature measurement,and its value reaches 5.81%K-1 at 342 K.The performance of Li2TiO3:Mn4+phosphor and Li2TiO3:Mn4+thin film for temperature field imaging on the surface of nickel circuit was compared.The results show that the Li2TiO3:Mn4+thin film can better reflect the true temperature distribution on the surface of nickel circuit.Furthermore,the Li2TiO3:Mn4+thin film also improves the temperature resolution of temperature imaging,showing more excellent temperature imaging performance.In the sixth chapter,the temperature properties of NaAl1-x-yScyP2O7:x Cr3+phosphor and their application prospect as near-infrared phosphor are ivestagated.Firstly,a series of NaAl1-x-yScyP2O7:x Cr3+(x=0-0.20,y=0-0.3)phosphors were synthesized by the method of solid-state reaction.Under 450 nm excitation,all samples exhibit broadband near-infrared emission of 600-1000 nm.Among them,NaAl0.92P2O7:0.08 Cr3+phosphor with the optimal luminescence was obtained,and its internal quantum efficiency reaches 70.96%.What’s more,the phosphor also has high thermal stability,whose integrated emission intensity at 420 K can maintain 71%of that at room temperature.Finally,the application prospect of the near-infrared phosphor in the field of plant lighting,night vision and nondestructive testing of biological tissues have been verified by the NaAl0.92P2O7:0.08 Cr3+near-infrared phosphor-converted LEDs(NIR pc-LEDs).Finally,the research work of this paper is summarized and prospected. |
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