Non-contact Temperature Research Articles

Prominent cryogenic fluorescence temperature sensing and superior room-temperature photochromism in Bi/Eu codoped KNN transparent-ferroelectric ceramics

The growing demand for the miniaturization and multifunctionality of optoelectronic devices has promoted the development of transparent ferroelectrics. However, it is difficult for the superior multiple optical properties of these materials to be compatible with the excellent ferroelectricity and piezoelectricity in transparent ceramics. Here, we successfully synthesized Bi/Eu codoped eco-friendly K0.5Na0.5NbO3 transparent-ferroelectric ceramics with photoluminescence (PL) behavior, photochromic (PC) reactions and temperature-responsive PL. Based on the distinct optical properties of ceramics at different temperature ranges (room temperature and ultralow temperature), high utilization of multiple optical functions was realized. At room temperature, the PC behavior induced PL modulation contrast reaches 75.2% (at 592 nm), which can be applied in the optical information storage field. In the ultralow temperature range, the ceramics exhibit excellent sensitivity (with a maximum relative sensitivity of 26.32%/K) via fluorescence intensity ratio technology and exhibit great application potential in noncontact optical temperature measurements. Additionally, the change in the PL intensity at different wavelengths (I614/I592) can serve as a reliable indicator for detecting the occurrence of the phase transition from rhombohedral to orthorhombic at low temperature. This work provides a feasible paradigm for realizing the integration of ferroelectricity and multifarious optical properties in a single optoelectronic material.

Multicolor luminescence and high efficient optical thermometric performance of Eu3+ and Sm3+ in self-activated Na2LuMg2V3O12 garnet

To develop efficient luminescence and optical thermometry materials for color display and non-contact temperature measurement, novel RE3+ (RE = Eu, Sm) doped self-activated Na2LuMg2V3O12 phosphors were prepared by a typical solid-state reaction method. Their crystal structure, morphology, multi-color luminescence and temperature sensing properties were elaborately investigated. Under UV light excitation, an intense and broad green-yellow emission band from VO43– group is observed in the Na2LuMg2V3O12 matrix, indicating its potential application in solid state lighting. After the incorporation of Eu3+ and Sm3+ ions, efficient energy transfer (ET) from VO43– group to Eu3+/Sm3+ ions occurs and the emission color of the samples can be readily tuned among different color ranges. Besides, based on the change of luminescence intensity and lifetimes of VO43– group in Na2LuMg2V3O12:Eu3+ and Na2LuMg2V3O12:Sm3+, the ET efficiency was analyzed and the mechanism is illustrated. Finally, large discrepancy between the thermal stability of VO43– group and Eu3+/Sm3+ ions are observed in the temperature-dependent emission spectra of Na2LuMg2V3O12:Eu3+ and Na2LuMg2V3O12:Sm3+. By taking advantage of the luminescence intensity ratio (LIR) between VO43– group and Eu3+/Sm3+ ions in Na2LuMg2V3O12:0.01Eu3+ and Na2LuMg2V3O12:0.07Sm3+, two new types of optical thermometry mediums were designed and their basic temperature sensing parameters were calculated.

Enhancing performance of microbolometers by utilizing low-temperature polycrystalline silicon

In response to the urgent need for advanced noncontact temperature sensing technologies to mitigate pandemic transmission, there has been a notable surge in global demand. Thermal cameras, combined with infrared sensors, are critical not only for high-resolution imaging but also for cost-effective commercialization. Amorphous silicon-based microbolometers offer advantages in terms of integration and cost compatibility with conventional silicon processes. However, they suffer from limitations in their electrical properties, particularly in the noise-equivalent temperature difference. This study examines the effectiveness of low-temperature polycrystalline silicon (poly-Si) as an active material for microbolometer cells compared to amorphous silicon, focusing on improving the temperature coefficient of resistance (TCR) and lowering the noise density. Our investigation reveals that various parameters, such as dehydrogenation temperatures ranging from 350 to 550 °C, diverse laser annealing techniques (including single, step and multishot methods), and laser power density levels ranging from 150 to 300 mJ/cm2, influence the grain size trends of poly-Si. Using these methods, we produced poly-Si films with grain sizes ranging from 15 to 40 nm, which were used as the active layer in bolometer cells. The final part of our study assessed the TCR and noise density in devices with different poly-Si grain sizes. The TCR/noise density ratio was 3.5 times better in poly-Si devices compared to amorphous silicon devices. This study evaluates poly-Si as an active material for microbolometers, paving the way for future research and development in next-generation infrared sensor technology.

Rb2InCl5·H2O doped with Te4+ for fluorescence thermometry and coordinated water-related structural phase transformation.

Here, we synthesized Rb2InCl5·H2O with x Te4+ doping by the coprecipitation method, which converts the original nonluminance for pure Rb2InCl5·H2O into orange luminescence ascribed to Te4+ incorporation with an emission peak at 648 nm and a full width at half maximum of 142 nm (420.3 meV) at room temperature. The photoluminescence (PL) lifetime of Te4+-doped Rb2InCl5·H2O exhibits a strong temperature dependence, with a maximum absolute sensitivity (SA) of 12 × 10-3 K-1 at 260 K and a relative sensitivity (SR) of 3.5%K-1 at 300 K, demonstrating its capability for non-contact remote temperature measurement. Additionally, we capture the dynamic changes of coordinated water with temperature in Rb2InCl5·H2O through temperature-dependent Raman spectroscopy, analyze the resulting structural phase transformation associated with coordinated water, and investigate the reversibility of this phase transformation.

Supernormal Temperature Sensing Performance Realized through the Blue Emitting Level of Er3+ along with Detection Ability in Deep Tissues.

Fluorescence intensity ratio (FIR)-type optical thermometers based on thermally coupled energy levels (TCLs) of rare earth ions are suitable candidates for noncontact temperature detection in living organisms, microelectronics apparatus, and so forth. Therefore, the improvement of the thermometric sensitivity of TCL-based thermometers has become a research hotspot in recent years. Herein, ultrahigh sensitivity and outstanding resolution for temperature sensing have been realized in YNbO4: Yb3+/Er3+. Unusually, the thermally coupled three-level system of Er3+: 4F7/2/2H11/2/4S3/2 is first employed for optical thermometry based on FIR technology. A supernormal thermometric sensitivity of 2.67% K-1 is obtained from the thermally coupled 4F7/2 and 4S3/2 states due to the large energy gap between them, significantly surpassing that of most temperature sensors in the same category. Furthermore, the existence of the intermediate level 2H11/2 can effectively prevent the decoupling effect between 4F7/2 and 4S3/2. Additionally, the temperature sensing behavior realized by the Stark sublevels of the Er3+: 4I13/2 → 4I15/2 transition, with a penetration depth of 8 mm, shows the potential of temperature measurement in deep biological tissues, benefiting from its excitation and emission wavelengths located in the biological window. All of the data reveal that YNbO4: Yb3+/Er3+ is an ultrasensitive optical thermometer and exhibits the capacity of temperature detection in deep tissues.

Thermodynamic Calculations of the Main Characteristics of the Combustion Process of Pyrotechnic Nitrate-Metallized Mixtures with Additives of Organic and Inorganic Substances under External Thermal Influences

The aim of the article is to determine the dependencies of the combustion product temperatures of four-component mixtures, the content of high-temperature condensate, and unoxidized metal on the excess oxidizer coefficient, the number of additives, and external pressure using thermodynamic calculations. Modern methods of physicochemical analysis (such as cinephotography and microcinephotography methods, X-ray analysis methods, non-contact and contact temperature measurement methods), nonlinear thermal conductivity and thermal stability methods, as well as mathematical and experimental-statistical modeling, were employed to investigate the influence of elevated heating temperatures (up to 800 K) and external pressures (up to 107 Pa) on the ignition and combustion processes of pyrotechnic products. Standard pyrotechnic equipment was used to test pyrotechnic product samples under specified conditions. Calculations based on models were conducted in real-time and dialog mode on computer devices that meet modern requirements for the use of specialized software. The results of thermodynamic calculations are presented for the dependencies of combustion product temperatures of multicomponent pyrotechnic mixtures based on powders of metal fuels (magnesium, aluminium), nitrate oxidizer (sodium nitrate), additives of organic and inorganic substances (paraffin, sodium fluoride), and the content of high-temperature condensate and unoxidized metal depending on the excess oxidizer coefficient α = 0.1…4.0, the amount of paraffin additive εp = 0…0.2, sodium fluoride additive εf = 0…0.06, and external pressure P = 105…107 Pa. Based on the obtained results of thermodynamic calculations, statistical models in the form of regression dependencies of the specified combustion characteristics on their technological parameters and external conditions have been developed. These models enable the determination of fire hazardous properties of mixtures in real-time dialog and PC-based scenarios, considering premature initiation of products based on them under external thermal actions.

Ultrasensitive and Adjustable Nanothermometers Based on Er3+-Sensitized Core@Shell Nanoparticles for Use in the First Biological Window.

In recent years, intensive research has focused on lanthanide-doped nanoparticles (NPs) used as noncontact temperature sensors, particularly in nanomedicine. These NPs must be capable of excitation and emission within biological windows, where biological materials usually show better transparency for radiation. In this article, we propose that NPs sensitized with Er3+ ions can be applied as temperature sensors in biological materials. We synthesized the NPs through a reaction in high-boiling solvents and confirmed their crystal structure and the formation of core@shell NPs by using X-ray diffraction, high-resolution transmission electron microscopy, and element distribution mapping within the NPs. NaErF4@NaYF4, NaYF4:12.5% Er3+, 2.5% Tm3+@NaYF4, NaYF4:7.5% Er3+@NaYF4, and NaYF4:12.5% Er3+, 2.5% Ho3+@NaYF4 exhibited intense upconversion (UC) emission under 1532 nm laser excitation detectable also in the whole human blood. We propose that this UC results from energy transfer between Er3+ ions and from Er3+ to Tm3+ or Ho3+ codopants. To determine the mechanism of UC, we measured the dependence of the emission band intensities on the laser power densities. Importantly, we also analyzed the temperature-dependent emission of the NPs within the 295-360 K range. Based on the collected emission spectra, we calculated the luminescence intensity ratios (LIRs) of the emission bands to assess their potential for optical temperature sensing. The temperature-sensing properties varied with the concentration of Er3+ ions and the presence of additional Tm3+ or Ho3+ codopants. Depending on the NP composition and the emission bands used for luminescence ratio calculations, the maximum relative temperature sensitivity ranged from 4.55%·K-1 to 1.12%·K-1, with temperature resolution between 0.05 and 2.53 K at room temperature. Finally, as proof of using NPs as temperature sensors in biomedicine, we successfully measured the temperature-dependent emission of NaYF4:7.5% Er3+@NaYF4 NPs dispersed in whole blood under 1532 nm excitation. We demonstrated that the ratio of Er3+ ion emission bands changes with temperature, indicating that these NPs have potential applications in temperature sensing within biological environments. We also confirmed the properties of NPs as temperature sensors by measuring the temperature reading uncertainty and the repeatability of the LIR readings during heating-cooling cycles, thereby confirming the excellent properties of the studied systems as temperature sensors.

Anti-thermal quenching and temperature sensing properties of Er3+/Yb3+ co-doped Sc2O3 phosphors

Up-conversion luminescence from rare earth doped phosphor is a potential candidate as non-contact temperature sensor. In this work, different Er3+ concentration doped Sc2O3: Er3+/Yb3+ phosphors were prepared through typical sol–gel method. The emission intensity reached the maximum as the doping concentration of Er3+ was 1.0 mol%. While, different from high concentration (0.5, 1.0 and 2.0) of Er3+ doped samples, an abnormal enhancement in the two green emissions and red emission in Sc2O3: 0.3 mol% Er3+/ 2 mol% Yb3+ phosphors was observed through elevate temperature and the enhancement factor reaches 1.3 as the temperature changed from 303 to 513 K. The reason for this concentration dependent thermal enhancement could be interpreted by the competition between increased energy transfer and non-radiative transition. The temperature sensing properties of samples, including relatively sensitivity, temperature resolution and repeatability were investigated and the maximum values reached 1.03 × 10−2 K−1 (303 K), 0.524 K (303 K) and 99.65 % (303––513 K), respectively, in Sc2O3: 1 mol% Er3+/2 mol% Yb3+ phosphors. The results imply that they have good temperature sensing ability and can be used as an optical temperature probe in research and production.

Ratiometric temperature sensing with non-thermally coupled levels from Pr–Al co-doped MgGa2O4

Fluorescence intensity ratio (FIR) technique demonstrates significant potential for non-contact temperature sensing with rapid response time, while the design of FIR probes is particularly intriguing. Herein, we report Pr–Al co-doped MgGa2O4 persistent luminescence nanoparticles (PLNPs), as MgAl0.04Ga1.96O4: 0.1 % Pr3+ (MAGP), for ratiometric temperature sensing application. Pr3+ ions function as the emission centers for dual-emission at 612 and 494 nm, while Al3+ ions adjust the lattice environment around Pr3+ ions to enhance the luminescence. Consequently, 274 nm excitation induces the emissions at 494 and 612 nm, as the transitions of Pr3+ for 3P0→3H4 and 1D2→3H4, respectively. The emission mechanism is substantiated by density functional theory calculations, regarding the electronic transitions of Pr3+. Ratiometric temperature sensing is achieved over the temperature range of 303–573 K with the thermally non-coupled mechanism of the 3P0/1D2 energy levels by FIR at 612 and 494 nm, respectively. The maximum relative sensitivity was 0.91 %. The mechanism is corroborated as the non-thermally coupled energy levels through intervalence charge transfer. Thus, the reversible and sensitive response was illustrated for temperature measurement and the non-thermally coupled mechanism is efficient for the design of ratiometric temperature sensors.

Modelling and Experimental Validation of the Flame Temperature Profile in Atmospheric Plasma Coating Processes on the Substrate

This work presents a characterisation model for the temperature distribution at different substrate depths during the atmospheric plasma spray (APS) coating process. The torch heat flow in this model is simulated as forced convection defined by a surface, a temperature profile, and a convection coefficient. The simulation model considers three plasma temperature profiles of the Al2O3 coating on a 5 mm thickness flat aluminium substrate. The simple and low-cost experimental procedure, based on a thermocouple, measures the plasma plume temperature distribution of the APS coating system, and their results are used to obtain the parameter values of each of the three proposed plasma temperature profiles. The experimental method for in situ non-contact temperature measurements inside the substrate is based on an infrared pyrometry technique and validates the simulation results. The Gaussian temperature profile shows excellent accuracy with the measured temperatures. The Gaussian approach could be a powerful tool for predicting residual stress through a coupled one-way thermal-mechanical analysis of the APS process.

Unraveling the photophysical response of BaLaLiTeO6:Dy3+ double perovskites with excellent thermal stability for colour tunable LEDs and optical thermometry

The quest for reliable phosphors has accelerated amidst a growing demand for cost-effective, high-performance multifunctional phosphors. Incorporating thermometric application into double perovskite phosphors can enhance their multifaceted features for diverse applications. The present work endeavours to develop a series of BaLaLiTeO6:Dy3+ double perovskites via a solid-state reaction route, stressing their application in next-generation colour-tunable LEDs and non-contact luminescence thermometry. X-ray diffraction, Raman and FTIR spectroscopy analysis were done to make inferences about the structural modifications induced by the substitution of Dy3+ at the La3+ site of BaLaLiTeO6. An extensive investigation of optical characteristics was carried out by diffuse reflectance spectroscopy, photoluminescence spectroscopy and decay curve analysis. Prominent photometric parameters were also evaluated to assess the commercial feasibility of the developed phosphors in photonic applications. Judd-Ofelt parameters were estimated from the photoluminescence excitation spectra of BaLaLiTeO6:Dy3+ for the first time. Furthermore, the values of radiative parameters, fluorescence decay time and quantum efficiency suggested the suitability of the developed phosphor as a competent material. A comprehensive analysis of BaLaLiTeO6:Dy3+ as a thermographic phosphor was done by temperature-dependent photoluminescence spectroscopy. The potential use of this material in luminescence temperature sensing was probed by estimating the thermometric figures of merit based on the fluorescence intensity ratio (FIR). An absolute sensitivity of 22.17 × 10−4 K−1 was achieved at a temperature of 500 K and a remarkable maximum relative sensitivity of 2.34 %K−1 was attained at 250 K, which is much higher than other Dy3+ substituted thermographic phosphors. All these culminated features of BaLaLiTeO6:Dy3+ phosphor proved their prospective applications in thermally stable colour-tunable LEDs, wLEDs and as non-contact optical temperature sensors.

Preparation and significant enhancement of upconversion luminescence of α-Ba2ScAlO5:Yb3+/Er3+ phosphors by Ca2+ ions doping

The intensity of upconversion luminescence (UCL) poses a significant challenge for oxides characterized by high phonon energy. Herein, a significant enhancement of red UCL is achieved through the introduction of an intermediate band (IB) in α-Ba2ScAlO5: Yb3+/Er3+ by Ca2+ ions doping. The absorption spectra verify the existence of the IB. The IB of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+ increases the host's absorption of excited photons, provides more electrons for the excitation of Er3+, and realizes the enhancement of UCL emission. The optimal concentration of Ca2+ in α-Ba2ScAlO5: 0.2Yb3+, 0.03Er3+ is 0.15. Compared with undoped Ca2+ samples, the red and green UCL intensity of α-Ba2ScAlO5: Yb3+, Er3+, 0.15Ca2+ increased by 48.2 and 10.6 times, respectively. The mechanism of Ca2+ enhanced UCL was investigated by analyzing the UCL spectra, absorption spectra and lifetime decay curves of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+. The temperature-dependent UCL properties of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+ were also studied by the 2H11/2 (525 nm) and 4F9/2 (667 nm) energy level radiation transitions. The observed linear correlation between luminescence intensity and temperature, coupled with its high sensitivity, indicates the promising potential for temperature sensing applications. This study not only opens a new avenue for enhancing UCL but also holds significant implications for sparking widespread interest in non-contact temperature sensing applications leveraging UCL.

TEMPERATURE MONITORING FOR LASER METAL DEPOSITION USING NEAR-INFRARED SPECTROSCOPY

Temperature monitoring during laser metal deposition (LMD) aids process control to ensure high-quality production. However, the fluctuating emissivity of the melt pool limits the accuracy of the existing non-contact temperature measuring devices. Thus, this work explores a new temperature monitoring technique, where the thermal radiation emitted by the processing zone was collected with a near-infrared (NIR) spectrometer and fitted to Planck's law to determine the temperature. This work has established the optimised angle and distance of the fiber probe from the LMD processing area to maximise the spectral signal acquisition. The temperature determined from the technique was cross-validated with a thermocouple, resulted in a small deviation of 2.39%. The applicability of the spectroscopic method for continuous temperature monitoring of the LMD process has been demonstrated. The optimised placement for the fiber probe end was determined at the 45˚ angle relative to the surface of the substrate and positioned 5 cm away from the molten pool. The temperature during the LMD process decreased gradually then stabilised after approximately 17 mm track length, resembling those reports in prior studies. Our findings support the practicality of the proposed temperature monitoring approach in LMD.

Temperature distribution inversion in infrared multispectral imaging based on ensemble network.

Temperature distribution can be acquired through non-contact temperature measurement using multispectral imaging. However, the challenge lies in radiometric temperature inversion owing to the unknown emissivity. Despite the promising results demonstrated by traditional algorithms and neural networks, enhancing the precision and reliability of temperature inversion remains a challenge. To tackle these challenges, in this work, we propose the use of ensemble learning for temperature distribution inversion in infrared multispectral imaging. The network comprises a base-learner and a meta-learner, trained to establish the nonlinear relationship between temperature and multispectral distribution measurements. Moreover, the network architecture exhibits high robustness against noise arising in the testing environment. Simulations and real experiments on multispectral imaging measurements illustrate that ensemble learning can be a potent tool for multispectral imaging radiation temperature distribution measurement, achieving superior inversion performance compared to other neural networks. The reproducible code will be available at https://github.com/shuowenyang/Temperature-Inversion.

Low temperature sensing using photoluminescence of carbon quantum dot-based PVA film

In recent years, non-contact temperature reading sensors based on carbon quantum dots (CQDs) have attracted a lot of attention, most researchers have studied them at room temperature and high temperature. In this paper, red-CQDs (R-CQDs) was synthesized by hydrothermal method using o-phenylenediamine and chemically characterized by transmission electron microscopy, Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The bandgap energy of R-CQDs was calculated from the absorption spectra, and the photoluminescence (PL) spectra at different laser powers showed that the PL of the R-CQDs were single-photo absorbing process. For better application, R-CQDs/polyvinyl alcohol (PVA) films were prepared. The PL properties of the film were studied. Experiments show in temperature range of 190∼260 K, the PL intensity decreases linearly with increasing temperature. Relative sensitivities of temperature sensing were calculated to be about −0.62% K−1. This work demonstrates the feasibility of its application in low temperature sensing.

Synthesis and upconversion color Tunability luminescence of K5Yb(MoO4)4 phosphor doped with Er3+and optical temperature sensing applications

A series of double molybdates with palmierite-related structure phosphors K5Yb1-x (MoO4)4:xEr3+ were synthesized by a solid-state method. It has been demonstrated that the K5Yb1-x (MoO4)4: xEr3+ phosphors are capable of exhibiting the characteristic green and red UC emission of Er3+ ions with excitation at 980 nm. Moreover, the green light emission is far more than the red light emission, so that the sample emits a powerful green light, which belongs to the two-photon absorption process. The upconversion efficiency is peaked when the content of Er3+ ions is 10 mol %. The optical thermometry properties of phosphors were explored by observing that the green UC emission intensity is temperature dependent. The maximum sensor sensitivity of the studied phosphor was discovered to be about 1.61%K−1 at the optimum doping concentration. And the phosphor is demonstrated to have high thermal stability by temperature cycling test. Eventually, a green light-emitting diode device was realized by using synthesized particles and a 980 nm near-infrared chip, which can emit a more obvious green light when the voltage reaches 1.80 V and the current can reach 800 mA, thus confirming its applicability in solid-state lighting. And the LED devices have been tested for life stability with little or no light degradation. These properties make the phosphors not only suitable for non-contact optical temperature measurement, but also able to be applied to solid state lighting.

Background radiation compensation calibration method for film cooling infrared temperature measurement based on BP neural network

The precise non-contact temperature measurement method is essential for studying gas turbine component heat transfer. While infrared thermal imaging provides high-resolution two-dimensional temperature fields, errors arise from the measurement environment's complexity, emissivity variations, and reflection radiation effects. This study utilizes BP neural networks to correct infrared radiation on gas film cooled plates. By modeling background radiation and analyzing infrared emission processes, factors influencing temperature distribution are identified. Experimental data from uncooled plate are used for network training. Experimental measurements were conducted on uncooled plates to obtain training data. A BP neural network was established based on Planck's law and the radiation transmission process to relate the mainstream temperature to the background radiation. Calibration analysis was performed based on experimental data from the cooled plate, achieving the restoration of the two-dimensional temperature field under multiple operating conditions and significantly reducing measurement errors. This method comprehensively considers the entire process of radiation transmission, thereby eliminating background radiation embedded in the infrared images. The obtained measurement results vividly depict the real temperature distribution, offered significant support for gas turbine engineering applications.

Cation-substitution-induced high spectral tunability and thermosensitivity in double halide perovskite Cs2InCl5∙H2O

The advancement of non-contact temperature measurement has brought about significant interest due to its rapid response, broad applicability, and minimal thermal inertia. However, challenges such as spectral peak position modulation, sensitivity improvement, and reliable performance enhancement continue to persist in this field. In this study, a double halide perovskite single-crystal Cs2InCl5∙H2O was synthesized, with the introduction of Bi3+ ions modulating the photoluminescence from orange to blue. Meanwhile, the deep-blue emission peaked at 410 nm, boasting a high photoluminescence quantum yield (PLQY) of nearly 46 % under 340 nm excitation. Furthermore, by incorporating varying concentrations of Bi3+ ions, two distinct emission peaks were generated, facilitating effective signal differentiation for temperature detection. Utilizing the thermal quenching responses of these two emission peaks, a temperature-detection methodology based on the fluorescence intensity ratio (FIR) was developed, using donor-acceptor pair emission as detection signals and self-trapped emission as reference signals. The designed Cs2InCl5∙H2O:0.07Bi3+ exhibits a maximum Sa of 0.082 K-1 and Sr of 3.349 %K−1, respectively. The spectral adjustability and high sensitivity achieved through cation-substitution strategy in this study offer a promising pathway for the development of advanced optical thermometry materials with enhanced performance characteristics.

A Noncontact Feed Microwave Temperature Sensor for Industry Device Based on Metamaterial

A Noncontact Feed Microwave Temperature Sensor for Industry Device Based on Metamaterial

A novel single near-infrared luminescence of negative thermal quenching materials for optical temperature measurement

In recent years, upconversion (UC) luminescence has gained attention due to its unique optical properties, and the thermal response spectral characteristics of these materials have been widely utilized in various fields including temperature sensing and biomedical research. However, the photoluminescence (PL) intensity of most rare earth ions doped phosphors decreases with increasing temperature, and the visible fluorescence emission penetration is still limited. In the work, the pure phase of Yb3+ and Er3+ ions co-doped Sc2Mo3O12 was successfully prepared. The Sc2Mo3O12: Yb3+, Er3+ sample showed a single emission of UC near-infrared (NIR) light. The optimum doping concentrations of 0.2 for Yb3+ ions and 0.01 for Er3+ ions were achieved. The possible upconversion luminescence (UCL) mechanism was investigated by analysing the UCL spectra, the down-shift (DS) excitation and emission spectra of Sc2Mo3O12: Yb3+, Er3+ phosphor. The excitation path of NIR emission is mainly through Er3+ from 2H11/2 to 4I9/2 energy level. What's more, the temperature-dependent near-infrared UCL properties of sample is explored in the temperature range from 323 K to 673 K. The enhancement of upconversion luminescence intensity shows a linear relationship with increasing temperature. The study paves a new way for non-contact optical temperature measurement with single near-infrared UCL emission.