Synthesis And Luminescence Properties Of The Optical Temperature Sensing Materials Based On Different Modes

The measurement of temperature?T?is important in both the scientific and industrial fields.In general,the traditional contact temperature measurement technology needs the heat transfer between the sensor and the object to achieve the heat balance.But this kind of temperature measurement usually takes a long time,which may change the actual temperature of the sample,especially if the size of the sample is comparable or smaller to the sensor.Therefore,it is very important to realize the temperature measurement of high temperature spatial resolution.In recent years,a new type of contactless temperature sensor,the optical temperature sensor,has attracted much attention because of its wide application in anti electromagnetic interference and thermal harsh environment.In this paper,different optical temperature sensing materials are synthesized by different methods.The study of temperature sensing performance based on fluorescence intensity ratio,lifetime and double emission center is of great significance for driving the application of phosphor materials in the field of temperature sensing.The Gd₂ZnTiO₆:Yb³⁺/Er³⁺phosphors(abbreviated as GZT:Yb³⁺/Er³⁺)have been successfully prepared by means of the sol-gel method.The GZT:Yb³⁺/Er³⁺phosphor exhibits intense green upconversion?UC?emission bands near 525/547 nm(²H_11/2/⁴S_3/2?⁴I_15/2)and weak red UC emission band near 663 nm(⁴F_9/2?⁴I_15/2)upon the 980 nm laser excitation.Furthermore,the sample emits near-infrared centered at 1527 nm associated with ⁴I_13/2?⁴I_15/2transition of Er³⁺ions.The high thermal activation energy?0.34 eV?of the GZT:Yb³⁺/Er³⁺phosphor is determined via the temperature dependent luminescence spectra upon the 980 nm laser excitation?low power density:0.8W/cm²?.Two thermally coupled levels(²H_11/2/⁴S_3/2)for Er³⁺using the fluorescence intensity ratio?FIR?technology were studied in detail.The maximum absolute sensitivity?90.11×10^-44 K^-11 at 539 K?of the targeted phosphor is determined from the experimental results.All results demonstrate a potential of application of as-prepared GZT:Yb³⁺/Er³⁺phosphors in optical thermometry.The color-tunable upconversion?UC?emission and optical temperature sensing based on non-thermal coupled levels?NTCL?were observed from the Yb³⁺/Ho³⁺codoped Lu₃NbO₇phosphors synthesized by the solid-state method.The phosphors are capable of generating color tunable UC luminescence from green?yellow?to yellow?green?with the increase of the Yb³⁺(Ho³⁺)concentration.The tunable emission is due to the different energy back transfer processes from Ho³⁺to Yb³⁺.The temperature sensing performances are investigated in the temperature range of 293-523 K based on NTCL by using fluorescence intensity ratio technology.The maximum absolute sensitivities are 0.37%K^-1,0.94%K^-1,0.27%K^-11 at 298K,which are based on three pairs NTCL of?⁵F₄/⁵S₂?⁵I₈?/?⁵F₅?⁵I₈?,?⁵F₅?⁵I₈?/?⁵F₄/⁵S₂?⁵I₇?and?⁵F₄/⁵S₂?⁵I₈?/?⁵F₄/⁵S₂?⁵I₇?of Ho³⁺,respectively.The above results suggest that the as-prepared Lu₃NbO₇:Yb³⁺/Ho³⁺phosphors have great potential for the application prospects of upconverter,color tunable device and optical temperature sensor.Mn⁴⁺and Sm³⁺singly doped and Mn⁴⁺/Sm³⁺codoped CaGdMgSbO₆?abbreviated as CGMS?double perovskite type phosphors have been successfully prepared by the solid-state reaction.X-ray powder diffraction and luminescence spectra were used to analysis their crystal phases and optical properties.Emissions of Mn⁴⁺and Sm³⁺in the visible region can be observed under 406 nm excitation,the luminescence mechanism of Mn⁴⁺and Sm³⁺in double perovskite CGMS phosphors was investigated.In particular,temperature-dependent luminescence spectra of the CGMS:Mn⁴⁺/Sm³⁺phosphor were measured at a large temperature range of 298-573 K.Mn⁴⁺and Sm³⁺possess different trends where the luminescence intensity of Mn⁴⁺ions decreases much more rapidly compared to that of Sm³⁺ions as the temperature increases.Accordingly,based on the fluorescence intensity ratio?FIR?between the two activator Mn⁴⁺and Sm³⁺,the optimal relative sensitivity of temperature sensing in the CGMS:Mn⁴⁺/Sm³⁺sample could reach 1.54%K^-11 at 473 K.This indicates that this CGMS:Mn⁴⁺/Sm³⁺material is a promising candidate for FIR-type optical temperature sensing.