Synthesis Of Rare Earth Doped Tungsten Molybdate Luminescent Materials And Study On Their Temperature Sensing Properties

In the international unit system,as one of the basic physical quantities,the importance of temperature for scientific research,industrial production and even daily life is self-evident.At present,most of the common temperature measurement methods are contact temperature measurement,but contact temperature measurement is easy to be affected by the surrounding environment,for example,in some strong magnetic field environment,it is easy to be affected by magnetic field and interfere with the measurement results,in the wind tunnel model,it is not easy to contact objects,so the measurement is not accurate,in these environments,contact temperature measurement will have some inherent limitations.The non-contact temperature measurement generally uses non-electrical signals and does not need to touch the object directly in the process of temperature measurement,so it can overcome the above shortcomings.Non-contact temperature measurement based on fluorescence spectrum has attracted more and more attention because of its wide temperature measurement range and high accuracy.in many materials that can be used for non-contact temperature measurement(such as quantum dots,organic dyes,rare earth doped fluorescent materials,etc.),rare earth doped fluorescent materials have the advantages of high luminous efficiency and low cost of excitation source,so it has attracted more and more scholars’ research.However,the rare earth doped fluorescent materials still have some shortcomings in temperature measurement,such as the stability and sensitivity of the materials need to be further improved.In order to solve the above problems,tungstate molybdate,a matrix material with high light transmittance,good self-luminescence and good thermal stability,was selected as fluorescent matrix material,and three kinds of rare earth doped fluorescent materials were designed,and its luminous properties and temperature-sensitive properties are studied,the main contents are as follows:1.In the first part,a series of MgMoO4:x%Er3+phosphors were prepared by high temperature solid state method.The Er3+doping concentration was optimized,the quenching mechanism of Er3+concentration was studied,and the temperature sensitive properties of the samples with the best doping concentration were studied.In this sample,the temperature dependence of the thermal coupling energy levels(2H11/2+4I15/2 and 4S3/2→4I15/2)of Er3+is used.Using the temperature measurement method of fluorescence intensity ratio,the absolute sensitivity and relative sensitivity of the sample are calculated according to the definition formula of sensitivity,and the maximum relative sensitivity is SR=0.83%K-1.The addition of charge compensator can keep the sample electrically neutral,thus improving the luminous efficiency of the sample.Therefore,we add a certain amount of charge compensator(Li+,Na+,K+)to the reactant to explore the effect of charge compensator on the luminescence properties of the sample.The temperature sensitive properties of the sample are studied by the same method,and the maximum relative sensitivity is SR=0.89%K-1.Finally,the sample is tested by cold-thermal cycle,and the results show that the material has excellent reversibility and repeatability.It shows that MgMoO4:x%Er3+phosphor has potential application value in the field of temperature sensing.2.In order to further obtain more sensitive fluorescent materials,a series of NaLaCaWO6:x%Eu3+phosphors were prepared by high temperature solid state method in the second part.We find that the abnormal thermal quenching occurs at the edge of the excitation spectrum of the sample,which is due to the fact that with the increase of temperature,the vibrational energy level of the ground state is thermally activated,the electron can jump up from the vibrational energy level of the ground state to the excited state,and the frequency of photons decreases.It shows a redshift in the spectrum,which leads to the abnormal thermal quenching at the edge of the charge transfer band.Based on this phenomenon,a temperature measurement method of fluorescence intensity ratio based on abnormal thermal quenching at the edge of charge transfer band in excitation spectrum is proposed.The maximum relative sensitivity of the sample has been reached.SR=2.23%K-1,the thermal cycle diagram shows that the material has good reversibility and repeatability.It shows that NaLaCaWO6:x%Eu3+phosphor has great application value in the field of temperature sensing.3.At present,there are few temperature sensitive materials that can be used to measure temperature in near infrared region,so in the third part,Pr3+ doped KLa(MoO4)2 phosphors were prepared by high temperature solid state method..Because Pr3+has rich energy levels,the sample has good luminescence in the near-infrared region,and the fluorescence temperature-sensitive properties of the samples in the near-infrared region are studied.At the same time,the phenomenon of abnormal thermal quenching at the edge of the charge transfer band similar to that in the previous chapter was found,and the temperature sensitivity of the sample in the visible region was investigated by using the excitation spectrum.Finally,the maximum relative sensitivity is SR=0.16%K-1 in the near infrared region and SR=1.17%K-1 in the visible region.Finally,through the hot and cold cycle,it is proved that the material has good reversibility and repeatability.This part makes a preliminary exploration on the temperature sensing materials which can be used in the near-infrared region.