Studies On Double Perovskite Luminescent Materials Based On Indoor Plant Lighting And Temperature Sensing

Indoor plant cultivation,which is protected from severe weather and allows plants to grow steadily,is emerging as a powerful solution to global food problems.Light not only provides energy for plant growth,but also affects the whole process of plant growth.In order to regulate the growth cycle of plants and improve the yield and quality of crops,the artificial light source used in houseplant cultivation has become an important production condition.Temperature is also another factor affecting the growth of indoor plants,and it is particularly important to accurately measure the temperature during the growing period.Traditional contact thermometers include:liquid thermometers,thermocouple thermometers,thermal resistance thermometers.But these traditional thermometers can not meet some special environment for accurate temperature measurement,such as biological cell growth,strong electromagnetic field,electronic circuit and other special environment.The limitation of traditional contact temperature sensor makes us urgently need to explore a non-contact optical temperature measurement technology with fast response,high accuracy,small temperature resolution and miniaturization to solve the problems faced by traditional temperature sensor.The method of temperature measurement using luminescent materials with fluorescent temperature-sensitive properties has been paid more attention.Therefore,this paper designed and prepared three kinds of tellurite phosphors with single manganese ions,co-doped manganese ions and rare earth ions,and explored their applications in indoor plant lighting and temperature sensing based on their luminescence properties and temperature sensitive properties.The main research contents are as follows:In the first part,a series of red phosphors SrLaLiTe_1-xO₆:x Mn⁴⁺were successfully synthesized by high temperature solid phase method.The structure of SrLaLiTeO₆ is cubic double perovskite structure,and its band gap energy Eg is 3.22 e V calculated from first principles,which is close to the experimental calculation of 3.08 e V.The emission spectra showed a narrow emission band ranging from 650 nm(15384 cm^-1)to 770 nm(12987 cm^-1),with peaks at 696 nm and 708 nm,which overlaps with the absorption spectra of photosensitive pigments P_R and P_FR in plants.When the Mn⁴⁺concentration is0.012,the excitation and emission intensity reach the maximum,and then the concentration quenching occurs.The results show that the quenching mechanism of Mn⁴⁺ion concentration in SrLaLiTeO₆ matrix is electric dipole-electric dipole interaction.When excited at 323 nm and 468 nm at 423 K,the integral intensity is still as high as79.01%and 81.44%,respectively.At 323 nm and 468 nm excitation,the calculated values of activation energy?E are 0.212 e V and 0.208 e V,respectively,indicating that the experimentally prepared samples have good thermal stability.All these results indicate that SrLaLiTe_1-xO₆:Mn⁴⁺has potential application value in plant lighting.In the second part,a novel double perovskite SrLaLiTeO₆:Mn⁴⁺,Dy³⁺phosphors were prepared by high temperature solid-state reaction method.The spectra show the double luminescence characteristics of Mn⁴⁺and Dy³⁺.Based on the different thermal quenching characteristics of Mn⁴⁺and Dy³⁺and the decay life of Mn⁴⁺,a two-mode optical temperature measurement method with high sensitivity and wide temperature range is realized.According to the fluorescence intensity ratio(FIR)of Dy³⁺(⁴F_9/2?⁶H_13/2)and Mn⁴⁺(²E_g?⁴A_2g),the decay lifetime of Mn⁴⁺(²E_g?⁴A_2g),we studied the temperature-sensitive properties in the range of 298?673 K.The maximum relative sensitivity(S_R)of SrLaLiTeO₆:0.012Mn⁴⁺,0.07Dy³⁺phosphors at the excitation of 351 nm and 453 nm are 1.60%K^-1@673 K and 1.44%K^-1@673 K respectively.The maximum values of S_R based on lifetime were 1.158%K^-1@673 K and 1.104%K^-1@673K,respectively.These results indicate that SrLaLiTeO₆:Mn⁴⁺,Dy³⁺phosphors have a good application prospect in optical thermometers,and provide useful guidance for the design of high sensitivity multimode optical thermometers.In the third part,a dual-mode optical temperature measurement method based on FIR and lifetime attenuation for SrGdLiTeO₆(SGLT):Mn⁴⁺/Eu³⁺phosphor is constructed.SrGdLiTeO₆ perovskite-type double-doped Mn⁴⁺,Eu³⁺phosphors were obtained by high temperature solid-state reaction method.At 302 nm excitation,the emission intensity of Mn⁴⁺decreases faster than that of Eu³⁺with the increase of temperature.Therefore,due to the different thermal quenching modes of Mn⁴⁺and Eu³⁺,the obtained phosphors exhibit excellent temperature-sensitive properties.The maximum absolute sensitivity and relative sensitivity calculated by Mn⁴⁺/Eu³⁺FIR is as high as 9.46%K^-1 and 4.9%K^-1@550 K,respectively.In addition,the lifetime attenuation of Mn⁴⁺can be used for temperature sensing,and the maximum relative sensitivity is 0.229%K^-1@573 K.These results indicate that SrGdLiTeO₆:Mn⁴⁺,Eu³⁺phosphors have broad application prospects in temperature measurement,and provide guidance for the exploration of high sensitivity temperature sensors.