Bi^(3+)-activated dual-wavelength emitting phosphors toward effective optical thermometry

Optical thermometry as an important local temperature-sensing technique,has received increasing attention in scientific and industrial areas.However,it is still a big challenge to develop luminescent materials with self-activated dual-wavelength emissions toward high-sensitivity optical thermometers.Herein,a novel ratiometric thermometric strategy of Bi^(3+)-activated dual-wavelength emission band was realized in the same lattice position with two local electronic states of La_(3)Sb_(1-x)Ta_xO_(7):Bi^(3+)(0≤x≤1.0)materials based on the different temperature-dependent emission behaviors,benefiting from the highlysensitive and regulable emission to the coordination environment of Bi^(3+).The structural and spectral results demonstrate that the emission tremendously shifted from green to blue with 68 nm and the intensity was enhanced 2.6 times.Especially,the visual dual-wavelength emitting from two emission centers was presented by increasing the Ta^(5+)substitution concentration to 20%or 25%,mainly originating from the two local electronic states around the Bi^(3+)emission center.Significantly,the dual-wavelength with different thermal-quenching performance provided high-temperature sensitivity and good discrimination signals for optical thermometry in the range between 303 and 493 K.The maximum relative sensitivity reached 2.64%/K(La_(3)Sb_(0.8)Ta_(0.2)O_(7):0.04Bi^(3+)@383 K)and 1.91%/K(La_(3)Sb_(0.75)Ta_(0.25)O_(7):0.04Bi^(3+)@388 K).This work reveals a rational design strategy of different local electronic states around the singledoping multiple emission centers towards practical applications,such as luminescence thermometry and white LED lighting.

Dual‑functional application of Ca_(2)Ta_(2)O_(7):Bi^(3+)/Eu^(3+)phosphors in multicolor tunable optical thermometry and WLED

A series of Bi^(3+)/Eu^(3+)co-doped Ca_(2)Ta_(2)O_(7)(CTO:Bi^(3+)/Eu^(3+))phosphors were prepared by high-temperature solid-state method for dual-emission center optical thermometers and white light-emitting diode(WLED)device.By modulating the doping ratio of Bi^(3+)/Eu^(3+)and utilizing the energy transfer from Bi^(3+)to Eu^(3+),the tunable color emission ranging from green to reddish-orange was realized.The designed CTO:0.04Bi^(3+)/Eu^(3+)optical thermometers exhibit signifcant thermochromism,superior stability,and repeatability,with maximum sensitivities of Sa=0.055 K^(−1)(at 510 K)and Sr=1.298%K^(−1)(at 480 K)within the temperature range of 300−510 K,owing to the diferent thermal quenching behaviors between Bi^(3+)and Eu^(3+)ions.These features indicate the potential application prospects of the prepared samples in visualized thermometer or hightemperature safety marking.Furthermore,leveraging the excellent zero-thermal-quenching performance,outstanding acid/alkali resistance,and color stability of CTO:0.04Bi^(3+)/0.16Eu^(3+)phosphor,a WLED device with a high Ra value of 95.3 has been realized through its combination with commercially available blue and green phosphors,thereby demonstrating the potential application of CTO:0.04Bi^(3+)/0.16Eu^(3+)in near-UV pumped WLED devices.

Multi-ratio optical thermometry and energy storage characteristics of Yb^(3+)/Er^(3+)/Tm^(3+)doped BaNb_(2)O_(6)transparent glass-ceramics

In order to meet the needs of new materials gradually developing towards miniaturization,integration,and light weight,multifunctional BaNb_(2)O_(6):Yb^(3+)/Er^(3+)/Tm^(3+)transparent glass-ceramics were success-fully prepared by melt quenching and controllable crystallization.Its structure,luminescence,and en-ergy transmission were studied.Using the opposite temperature dependence of the Tm^(3+)emission band and the corresponding large energy level gap,a maximum relative sensitivity of 2.3%K^(-1)based on thermal coupling levels(TCLs)is obtained in a wide temperature range(298-673 K).The multi-ratio optical thermometry based on TCLs and non-TCLs is successfully realized by using the different emission bands of double emission centers,which makes it possible for self-reference optical temperature measurement modes.In addition,the transparent glass-ceramic exhibits excellent electrical properties under 700 kV cm^(-1)electric field:high discharge energy density(W_(d)=0.99 J cm^(-3)),huge instantaneous power density(225.3 MW cm^(-3)),and ultra-fast discharge rate(T_(0.9)≤15.8 ns).The prepared glass-ceramic is expected to be a new type of lead-free multifunctional photoelectric material for temperature sensors and transparent electronic devices.

Te^(4+)-doped Cs_(2)InCl_(5)·H_(2)O single crystals for remote optical thermometry

Zero-dimensional metal halide perovskites have captured intense research interest owing to their unique optoelectronic properties.Particularly,metal halides with the ns^(2) electronic configuration are of great interest owing to the high-temperature sensitivity of their photoluminescence,which could be applied to remote optical thermometry(ROT).Herein,all-inorganic and lead-free halide perovskite Te^(4+)-doped Cs_(2)InCl_(5)·H_(2)O single crystals(SCs)were prepared through the hydrothermal method and showed a strong temperature dependence of photoluminescence lifetime.Upon Te^(4+) doping,the nonemissive Cs_(2)InCl_(5)·H_(2)O SC exhibits a bright orange emission at 660 nm with a wide full width at half maximum of 180 nm.The strong phonon-exciton coupling promotes the formation of self-trapped excitons in the soft lattice of the zero-dimensional Te^(4+)-doped Cs_(2)InCl_(5)·H_(2)O SC.The Te^(4+) ions with the 5 s^(2) electronic configuration endow the Te^(4+)-doped Cs_(2)InCl_(5)·H_(2)O SC with a strong temperaturedependent photoluminescence lifetime.This SC reaches a maximum specific sensitivity of 0.062 K^(-1) at 320 K,thereby showing the potential advantages of indium-based metal halide perovskites in ROT applications.

Spectroscopic and temperature sensing properties of Sm^(3+) in self-activated CsLu(WO_(4))_(2) phosphors

In this research,a series of Sm^(3+) doped CsLu(WO_(4))_(2) phosphors was prepared via high temperature solid phase technique to design new red phosphors and optical thermometric materials.Their structures,morphology,band gap and luminescence properties were characterized by X-ray diffraction,scanning electron microscopy,diffuse reflection and luminescence spectra,respectively.Under UV excitation,CsLu(WO_(4))_(2) gives rise to a blue broad emission band between 350 and 700 nm,which stems from the ^(3)T_(1u)→^(1)A_(1g) transition of WO_(6)^(6-) groups.When Sm^(3+) is introduced into CsLu(WO_(4))_(2),energy transfer between WO_(6)^(6-) groups and Sm^(3+) ions takes place in CsLu(WO_(4))_(2):Sm^(3+)phosphors,and color-tunable luminescence from blue to red is realized by controlling the Sm^(3+) doping concentration.The energy transfer efficiency between WO_(6)^(6-) groups and Sm^(3+) ons was analyzed,and the energy transfer mechanism was determined to be dipole-dipole interactions.According to the temperature-dependent luminescence spectra,WO_(6)^(6-)groups and Sm^(3+)ions exhibit large discrepancy in thermal quenching rates,and thus the temperature sensing properties of CsLu(WO_(4))_(2):Sm^(3+) in the temperature range of 283-403 K were analyzed.Based on the framework of fluorescence intensity ratio theory,the basic optical thermometry parameters including absolute and relative sensitivity of CsLu(WO_(4))_(2):Sm^(3+) we re calculated and the results show that it has great potential for application in optical thermometry.

Effect of radiative loss mechanisms on FIR thermometric parameters of Nd^(3+)-doped lithium tellurite glasses

Nd^(3+)-doped tellurite glasses are promising materials for thermometers based on the fluorescence intensity ratio(FIR)technique.Nevertheless,at high Nd^(3+)concentrations,energy transfer(ET)processes such as optical reabsorption and cross-relaxation can affect the Nd^(3+)emission,which has been little explored in the literature.Therefore,the present work investigated the use of Nd^(3+)-doped tellurite glass(samples doped with Nd^(3+)at 0.2 mol%,0.5 mol%,2.0 mol%,and 4.0 mol%)in fluorescence thermometers,in the temperature range from 299 to 371 K.The results indicate a strong dependence of the FIR parameters on the Nd^(3+)concentration,due to changes in the emission band profiles caused by optical reabsorption of the Nd^(3+)emissions and cross-relaxation processes.A decrease of the relative sensitivity of the ratio^(4)F_(5/2)→^(4)I_(9/2)/^(4)F_(3/2)→^(4)I_(9/2)is observed for samples doped with higher amounts of Nd^(3+).The maximum relative sensitivity at 299 K is 3.00%/K,which is the highest value among the reported Nd^(3+)ions.

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce^(3+)/Eu^(2+)co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.

Improving luminescence and thermometric performance of Ba_(2)CaWO_(6):Er^(3+) by tri-doping with Yb^(3+) and Na^(+)

The Er3+doped double perovskite Ba_(2)CaWO_(6) crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio(FIR) of transitions from ^(2)H_(11/2) and ^(4)S_(3/2) to the lowered ^(4)I_(15/2) level.However,the Ca^(2+) vacancy defect caused by the charge difference between rare-earth ions and the substituted alkaline-earth ions gives rise to the non-radiative probability and limits the thermal sensitivity.Here,the up-conversion luminescence and thermometric performance of Er^(3+),Yb^(3+) dopedBa_(2)CaWO_(6) are tuned by tri-doping with alkaline ions.The Ca^(2+) vacancy defect can be eliminated by the introduction of Na^(+),which occupies the Ca^(2+) site when it is doped into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+).On the contrary,the doping of Cs^(+) into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+) enhances the defect concentration because it occupies the site of Ba^(2+).Thus,the tri-doping of Na^(+) reduces the non-radiative probability and enhances the quantum efficiency of Er^(3+),leading to the improvement of the thermometric sensitivity of Ba_(2)CaWO_(6).As a result,we get an excellent thermometric Ba_(2)CaWO_(6):8%Yb^(3+),3.5%Er^(3+),6%Na^(+) powder with a luminescence lifetime of 515 μs and maximum thermal sensitivity(S_(r)) of 1.45%/K,which is more than three times higher than that of the BCWO:Er^(3+) powder.

基于调控Cr^(3+)锐线发射带宽的柔性光纤温度传感器

我们设计并制备了一种基于LiGa_(4)(MgGe)_(0.5)O_(8):Cr荧光粉变温发光特性的柔性温度传感光纤.通常来说,随着温度的升高,发光材料基质的电子-声子作用将加剧,这会导致其发射峰的半高宽(FWHM)在升温时不断加宽.在本工作中,随着LiGa_(5-x)(MgGe)_(x)O_(8):Cr中[Mg^(2+)-Ge^(4+)]化学单元成分比例的增加,荧光粉近红外发光的FWHM出现明显展宽,其外量子效率也从24.8%增加到50.0%.进一步研究发现,LiGa_(4)-(MgGe)_(0.5)O_(8):Cr纳米荧光粉的发光具有优异的热稳定性和温度传感特性,在443 K时绝对灵敏度可达7.51 cm^(-1)K^(-1),303 K下相对灵敏度为0.64%K^(-1).基于此,我们搭建了具有可重复性、高精度和优异稳定性的柔性全光纤系统,并将其用于实时监测物体的温度.本研究不仅探索了具有锐线发射的Cr^(3+)掺杂发光材料的应用,而且丰富了基于荧光材料带宽特性的光学测温新思路.

Luminescence properties of Eu3+doped YBO3 for temperature sensing

YBO3：2 at.% Eu3＋ was prepared by the solid state reaction and its temperature dependent luminescence was investigated for possible applications in temperature sensing. Phase composition of this material was confirmed by X-ray powder diffraction analysis and excitation and emission spectra were also provided. Under excitation of 355 nm, the fluorescence originating from 5D0 and 5D1 states varied as the temperature rose in a region from 333 to 773 K. The fluorescence intensity ratio （FIR） of SD0 and 5D1 was investigated which increased significantly with the rise of temperature. The maximal relative sensitivity in the whole temperature range was 1.8% K-1（at 333 K）. The results recommended YBO3：Eu3＋ as a new material of the FIR method for non-contact optical thermometry.

Luminescent and thermometric properties of dual emitting Eu^(2+)/Sm^(3+) co-doped Sr_(4)La(PO_(4))_(3)O phosphor based on energy transfer

Eu^(2+)/Sm^(3+)co-doped dual-emitting Sr_(4)La(PO_(4))_(3)O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu^(2+)/Sm^(3+)co-doped Sr_(4)La(PO_(4))_(3)O phosphors were researched and analyzed in detail.The blue emission of Eu^(2+)and the red emission of Sm^(3+)can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(^(3+))phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(3+)phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu^(2+)and Sm^(3+)ions.