Study Of Upconversion Luminescence And Temperature Sensing Behavior Of Rare Earth Doped Phosphates And Stannates

Rare-earth ion-doped upconversion luminescence is the use of anti-Stokes effect,that is,the use of multiple low-energy long-wavelength photons in succession to get a high-energy short-wavelength photons.Among the various rare earth ion-doped upconversion luminescent material systems,phosphates have high chemical and thermal stability and high emission quantum yield,low solubility in water,etc.Stannates have low phonon energy and good chemical and physical stability,etc.They are both studied in this paper.In this paper,Er³⁺/Yb³⁺co-doped upconversion luminescent materials are prepared by the high-temperature solid-phase method,and the relationship between the luminescence properties pumping power,the energy level transfer mechanism and temperature sensing properties are studied,respectively.The main results are as follows:(1)A series of Er³⁺/Yb³⁺co-doped Lu PO₄ upconversion luminescent materials were prepared by a high-temperature solid-phase method.Er³⁺and Yb³⁺ions replaced Lu³⁺into the lattice.The optimal Er³⁺ion doping concentration is 0.02 mol and Yb³⁺ion is 0.50 mol.The emission peaks of 525 and 552 nm in the green emission region belonged to ²H_11/2?⁴I_15/2 and ⁴S_3/2?⁴I_15/2,respectively.The peak of 669 nm in the red emission region is ⁴F_9/2?⁴I_15/2.The emission intensity was varied with pumping power.The slope values of the fitted curves n are 1.64,1.80 and 1.70,respectively,proving that a two-photon is involved in the upconversion emission process.The temperature sensing characteristics of the material were studied by using the fluorescence intensity ratio technique,in which the fit of the FIR scattering point is99.93%and the sensing function is FIR=4.33×exp(-966.89/T).The thermal coupling energy level difference is?E=671.93 cm^-1,and the maximum absolute sensitivity is1.068×10^-2 K^-1 at 463 K.(2)A series of Er³⁺/Yb³⁺and Er³⁺/Yb³⁺/Al³⁺co-doped La PO₄ upconversion luminescent materials were prepared by a high-temperature solid-phase method,It was found that rare-earth ions entered the lattice by replacing La³⁺by XRD patterns.The best doping concentrations were found to be Er³⁺=0.02 mol,Yb³⁺=0.50 mol,Al³⁺=0.04 mol,respectively.The emission peaks at 525 and 552 nm in the green emission region are from ²H_11/2 and ⁴S_3/2 back to the ground state,respectively.The peak 669 nm is from ⁴F_9/2?⁴I_15/2 energy level.The slope n of the fitted curve is not greater than 2,inferring that the material is two-photon involved in upconversion luminescence.The FIR fitted curve fit are 99.98%,FIR=6.22×(-1062.05/T).The maximum absolute sensitivity is 1.977×10^-2 K^-1 at 503 K,while FIR=6.10×exp(-1099.56/T),and the maximum absolute sensitivity is 1.843×10^-2 K^-1 at 553 K after doping with Al³⁺ions.The FIR values of the samples did not fluctuate much during the repeated temperature ramp-up and ramp-down.Therefore,the samples were considered to have good temperature stability.(3)Considering stannates with better luminescence intensity and lower phonon energy characteristics,a series of Er³⁺/Yb³⁺and Er³⁺/Yb³⁺/Mg²⁺co-doped Ca Sn O₃ were prepared by a high temperature solid phase method.Er³⁺/Yb³⁺ions have entered the matrix to replace Ca²⁺ions form the XRD patterns.The optimal doping concentration is Er³⁺=0.02 mol,Yb³⁺=0.10 mol,Mg²⁺=0.08 mol.The sample luminescence is improved after doping with Mg²⁺ions.The luminescence intensity of ²H_11/2?⁴I_15/2energy level at 530 nm is increased by 4.33 times,⁴S_3/2?⁴I_15/2 energy level at 552 nm is increased by 4.68 times and ⁴F_9/2?⁴I_15/2 energy level at 666 nm is increased by 1.33times after the introduce of Mg²⁺.The sample was a two-photon involved in the upconversion luminescence process.Process between Er³⁺and Yb³⁺ions in the Ca Sn O₃.The fitting function is FIR=13.41×exp(-1026.99/T),and the curve fit is99.94%.The calculated thermal coupling energy level pair energy difference is?E=713.702 cm^-1.The maximum absolute sensitivity is 9.537×10^-1 K^-1at 473 K.After doping with Mg²⁺ions,the FIR scatter fit curve is calculated to be 99.99%,and the fit function is FIR=8.46×exp(-945.50/T).The thermal coupling energy level pair energy difference is calculated to be?E=657.07 cm^-1.The maximum absolute sensitivity of the material is 4.136×10^-1 K^-1 at 433 K.The material was considered to have a good temperature stability.