The Study On Synthesis,luminescence And Temperature Sensing Of Rare-earth Optical Materials

The contact nature of the traditional contact thermometers makes the conventional thermometers not suitable for many cases due to the restriction of their intrinsic properties,such as in corrosive or electromagnetic interference environment,temperature sensing for tiny electronic device,cell or fast moving objects.As a result,it is of great significance to develop the non-contact temperature sensors with fast response,miniaturization,high sensitivity,and high resolution.In contrast to other thermometers,based on rare earth doped fluorescence temperature sensing materials possess the unique advantage,the fluorescence intensity ratio（FIR）technique is regarded as a very promising approach.Although the Optical sensors for Temperature is various,they are still some obstacles for application.So in this article,through the preparation of three kinds of rare earth doped materials,luminescence properties of the material is studied,and the luminescence intensity ratio based on excitation spectra is put forward to realize temperature sensing,which is expect to avoid the poor stability,narrow the scope of temperature,et al.The main contents and conclusions of this paper are as follows:Firstly,a series of color-tunable emitting LiSr_1-xVO₄:xEu³⁺phosphors are synthesized by solid state reaction.The Luminescence properties and temperature sensing performance are investigated.Under near ultraviolet（NUV）excitation,LiSr_1-xVO₄:xEu³⁺exhibits both the green broad band luminescence due to VO₄^3-groups and red sharp emission peaks of sensitized Eu³⁺ions.The tunable color of high-brightness emission from green to red are realized by controlling the Eu³⁺doping content.The optical thermometry of LiSr_1-xVO₄:xEu³⁺are studied via excitation intensity ratio between V-O charge transfer band and Eu³⁺f-f transition at low temperature（10-325 K）.The highest absolute sensitivity S_A is found to be 8.6%K^-1.The red emission intensity of Eu³⁺shows a linear relationship in high temperature range of 298-573 K.The maximum value of relative sensitivity S_R is established as2.2%K^-1@573 K.The LiSr_1-xVO₄:xEu³⁺phosphors might be a promising candidate for NUV based phosphor and temperature sensing in a wide temperature range.In addition,a series of novel red emission phosphors Sr₃Lu_1-x（VO₄）₃:xEu³⁺are synthesized successfully by traditional high-temperature solid state reaction.The excitation and emission spectra show that these samples can be effectively excited by near ultraviolet（NUV）light and then produce strong and pure red emission at 615 nm originated from ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺.The integral red emission intensity of Sr₃Lu_0.96（VO₄）₃:0.04Eu³⁺is 3 times higher than that of Y₂O₃:Eu³⁺.The abnormal thermal quenching phenomena are observed.The emission intensity of Eu³⁺ions originating from ⁵D₀ excited state declines with increasing temperature upon NUV excitation.It is caused by the thermally-activated absorption which is clearly proved by the temperature-dependent excitation spectra.Temperature sensing behaviors based on the fluorescence intensity ratio（FIR）technique between VO₄^3-and Eu³⁺（⁷F₀→⁵D₂）excitation along with the thermal-coupled energy levels of ⁵D₁ and ⁵D₀ are also investigated in the temperature range from 298 K to 573 K.The results indicate that it opens up new possibilities of pure intense red emitting phosphor and the phosphors could be a good candidate for ratiometric optical thermometry.Secondly,one class of highly luminescent lanthanide complexes with 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate（H₂BDC-F₄）as ligand have been synthesized and characterized.The solid-state europium complex（complex 7）exhibits intense red luminescence at around 615 nm via excitation of the ligand at room temperature.Meanwhile,the solid-state terbium complex（complex 1）shows strong green emission at around 544 nm,which illustrates that the organic ligand is more suitable to sensitize Tb³⁺ions.An efficient Tb³⁺to Eu³⁺energy transferability in the binuclear lanthanide compounds 2-6 have been observed.The luminescent color can be tuned from red to green by changing the ratio of Tb³⁺to Eu³⁺,which indicates them as promising light emitting materials potentially.The luminescent intensity ratio between Tb³⁺:⁵D₄→⁷F₅and Eu³⁺:⁷F₀→⁵D₂ decrease significantly with temperature in the binuclear lanthanide complexes.In temperature range of 50-300 K,the emission intensity ratio shows linear relationship with the increasing temperature.The largest relative sensitivity S_R is found to be 0.76%K^-1.It illustrates the binuclear lanthanide complexes could be served as potential optical thermometry materials.