Optical fiber temperature sensing device and method based on thermal coupling energy level

Abstract

The invention discloses an optical fiber temperature sensing device and method based on a thermal coupling energy level, and the device comprises an excitation assembly, a sensing assembly, and a detection assembly, the excitation assembly comprises an excitation light source which can emit 980nm infrared light, and is used for exciting a sensing material; the sensing assembly comprises a YVO: Yb / Er co-doped luminescent material and a temperature control device, and the YVO: Yb / Er co-doped luminescent material is fixed on the outer wall of the temperature control device through special resin glue, so that the YVO: Yb / Er co-doped luminescent material can synchronously change the temperature along with the temperature change of the temperature control device; the detection assembly comprises an optical fiber and a spectrograph. Therefore, by optimizing the doping proportion, the fixing mode and the signal analysis method of the YVO: Yb / Er material, the temperature sensing performance of the 313-363K interval is remarkably improved, especially the relative sensitivity and the measurement precision in the low-temperature area are excellent, and the temperature sensor can be widely applied to high-precision temperature monitoring in the fields of precision manufacturing, biomedical treatment and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature sensing, and in particular to a fiber temperature sensing device and method based on thermal coupling energy levels. BACKGROUND

[0002] Temperature measurement is one of the key technologies in the fields of industrial production, biological medicine, environmental monitoring, etc. Traditional temperature sensing methods (such as thermocouples, resistance thermometers) have problems such as being susceptible to electromagnetic interference, size limitation (difficult to use in small spaces or inside the body), slow response speed, etc., and are difficult to meet the high-precision measurement requirements in complex environments.

[0003] The fluorescence intensity ratio (FIR) temperature measurement technology is based on the thermal coupling energy level characteristics of luminescent materials. By analyzing the fluorescence intensity ratio of two thermal coupling energy levels at different temperatures, the temperature is inverted, which has the advantages of non-contact, anti-electromagnetic interference, high sensitivity, high spatial resolution, etc., and has become a research hotspot in recent years. The core principle is that the particle population of the thermal coupling energy level follows the Boltzmann distribution, and the fluorescence intensity ratio presents a certain functional relationship with the temperature. By calibrating this relationship, temperature measurement can be achieved.

[0004] Currently, fluorescence temperature measurement technology based on rare earth ion-doped materials has been widely studied. For example, Er³⁺ ions have a rich energy level structure (such as ²H 11 / 2 and 4 S3 / 2, etc. thermal coupling energy levels), which are often used as temperature measurement ions; Yb³⁺ as a sensitized ion can enhance the energy transfer efficiency and improve the fluorescence signal strength. However, the existing technology still has the following shortcomings: 1. The relative sensitivity of some rare earth-doped materials is low in the low temperature range (such as 300-400K), which limits their application in low-temperature high-precision temperature measurement scenarios; 2. The coupling mode of the material and the temperature control device (such as fixed mode, thermal conduction efficiency) has a great influence on the measurement accuracy, and the traditional fixed mode (such as mechanical clamping) is easy to cause temperature lag or unevenness; 3. The fitting accuracy and stability of the fluorescence intensity ratio and temperature need to be improved, and the temperature uncertainty of some materials exceeds 1K, which is difficult to meet the high-precision requirement.

[0005] In view of the above problems, the present application proposes a thermal coupling energy level fiber temperature sensing device and method based on YVO4:Yb³⁺ / Er³⁺ co-doped material, which significantly improves the relative sensitivity and reduces the temperature uncertainty in the range of 313-363K by optimizing the material doping ratio, improving the fixing mode and the signal analysis method, providing a solution for low-temperature high-precision temperature measurement. SUMMARY

[0006] The present application aims to at least partially solve one of the problems in the related art.

[0007] To this end, one object of the present application is to provide a fiber-optic temperature sensing device and method based on thermal coupling energy levels, which significantly improves the temperature sensing performance in the range of 313-363K by optimizing the doping ratio, fixing method and signal analysis method of YVO4:Yb3+ / Er3+ material, especially in the low temperature range, and has excellent relative sensitivity and measurement accuracy, and can be widely applied to high-precision temperature monitoring in the fields of precision manufacturing, biomedical treatment, etc.

[0008] To achieve the above object, the first aspect of the present application proposes a fiber-optic temperature sensing device based on thermal coupling energy levels, comprising an excitation component, a sensing component and a detection component, wherein the excitation component comprises an excitation light source capable of emitting 980nm infrared light for exciting the sensing material; the sensing component comprises YVO4:Yb3+ / Er3+ co-doped luminescent material and a temperature control device, the YVO4:Yb3+ / Er3+ co-doped luminescent material is fixed on the outer wall of the temperature control device by special resin glue, so that the YVO4:Yb3+ / Er3+ co-doped luminescent material can change temperature synchronously with the temperature change of the temperature control device; the detection component comprises an optical fiber and a spectrometer, one end of the optical fiber is used to receive the fluorescence signal generated after the YVO4:Yb3+ / Er3+ co-doped luminescent material is excited, and the other end is connected with the spectrometer to transmit the fluorescence signal to the spectrometer for detection and analysis.

[0009] The fiber-optic temperature sensing device and method based on thermal coupling energy levels of the present application significantly improve the temperature sensing performance in the range of 313-363K by optimizing the doping ratio, fixing method and signal analysis method of YVO4:Yb3+ / Er3+ material, especially in the low temperature range, and have excellent relative sensitivity and measurement accuracy, and can be widely applied to high-precision temperature monitoring in the fields of precision manufacturing, biomedical treatment, etc.

[0010] In addition, the fiber-optic temperature sensing device and method based on thermal coupling energy levels proposed above according to the present application can also have the following additional technical features: In one embodiment of the present application, the temperature control device is a constant-temperature magnetic stirrer, and the YVO4:Yb3+ / Er3+ co-doped luminescent material is fixed on the outer wall of the conical flask of the constant-temperature magnetic stirrer.

[0011] In one embodiment of the present application, the doping concentration of Er3+ in the YVO4:Yb3+ / Er3+ co-doped luminescent material is 1%-5%.

[0012] In one embodiment of the present application, the doping concentration of Er3+ in the YVO4:Yb3+ / Er3+ co-doped luminescent material is 2%, and the doping concentration of Yb3+ is 20%.

[0013] The first aspect of the present application provides a fiber temperature sensing method based on thermally coupled energy levels, including the following steps: The YVO4:Yb3+ / Er3+ co-doped luminescent material is prepared by a high-temperature solid-phase method, specifically including: Vanadium-containing compounds, ytterbium-containing compounds, erbium-containing compounds, and yttrium-containing compounds are weighed according to a proportion, the doping concentration of Er3+ is 1%-5%, and the doping concentration of Yb3+ is 10%-30%; The raw materials are put into an agate mortar and ground to be uniformly mixed; The mixed raw materials are put into a high-temperature furnace for pre-burning, the pre-burning temperature is 800-900℃, and the holding time is 4-6 hours; The pre-burning product is taken out, ground again, and then put into a high-temperature furnace for sintering, the sintering temperature is 1000-1200℃, and the holding time is 6-10 hours; After cooling, post-processing is performed to obtain the YVO4:Yb3+ / Er3+ co-doped luminescent material; The YVO4:Yb3+ / Er3+ co-doped luminescent material is fixed on the outer wall of a temperature control device by using special resin glue; The YVO4:Yb3+ / Er3+ co-doped luminescent material is excited by using a 980nm laser, and the excitation temperature range is 313-363K; The fluorescence signal generated by the YVO4:Yb3+ / Er3+ co-doped luminescent material is transmitted to a spectrometer by using an optical fiber, and the emission peaks of two main emission energy levels (2H 11 / 2 and 4 S3 / 2) of Er3+ are collected; The emission peaks are integrated and calculated to obtain a fluorescence intensity ratio (FIR), and the change of the fluorescence intensity ratio with temperature is fitted, the fitting meets the Boltzmann distribution, and temperature sensing is realized based on this.

[0014] In one embodiment of the present application, in the step, the center wavelengths of the two main emission energy levels (2H 11 / 2 and 4 S3 / 2) of Er3+ are respectively located at 525nm and 550nm.

[0015] In one embodiment of the present application, in the step, the fitting formula of the fluorescence intensity ratio (FIR) is FIR=Bexp(-C / T), wherein B is a fitting parameter, C is a constant related to the energy level difference of the two energy levels, and T is temperature.

[0016] In one embodiment of the present application, the relative sensitivity of the YVO4:Yb3+ / Er3+ co-doped luminescent material is 0.792 at 313 K.

[0017] In one embodiment of the present application, in the step, the temperature is controlled at 313-363 K by the temperature control device.

[0018] In one embodiment of the present application, in the step of “preparing YVO4:Yb3+ / Er3+ co-doped luminescent material”, the Er3+ doping concentration of the YVO4:Yb3+ / Er3+ co-doped luminescent material is 2%, and the Yb3+ doping concentration is 20%.

[0019] Compared with the prior art, the present application has the following advantages: (1) High sensitivity: the relative sensitivity is 0.792 at 313 K, which is 1.36 times higher than that of the traditional thermal coupling level temperature measurement, and is particularly suitable for low-temperature high-precision monitoring.

[0020] (2) Low uncertainty: the temperature uncertainty is ≤0.2 K, which is better than the existing infrared temperature measurement technology (1 K), and the measurement accuracy is significantly improved.

[0021] (3) Stable temperature coupling: the material is fixed by using special resin glue, which ensures that the material and the temperature control device are synchronized for temperature control, and reduces the temperature lag error.

[0022] (4) High fitting accuracy: the fitting goodness of the fluorescence intensity ratio and the temperature is R²=0.997, the fitting stability is high, and the calibration reliability is strong.

[0023] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by practicing the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings, in which: Figure 1 The overall control connection diagram of a fiber temperature sensing device and method based on thermal coupling energy level according to one embodiment of the present application; Figure 2 The energy level diagram of Yb and Er3+ according to one embodiment of the present application; Figure 3 The emission spectrum of YVO4:2%Er20Yb excited by a 980 nm laser according to one embodiment of the present application; Figure 4 The fluorescence intensity ratio of a fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application varies with temperature; Figure 5 The absolute sensitivity of a fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application varies with temperature; Figure 6 The relative sensitivity of a fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application varies with temperature; Figure 7 The temperature uncertainty of a fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application varies with temperature.

[0025] As shown in the figure: 1, excitation light source; 2, YVO4:Yb3+ / Er3+ co-doped luminescent material; 3, temperature control device; 4, optical fiber; 5, spectrometer. DETAILED DESCRIPTION

[0026] A fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application will be described below in conjunction with the accompanying drawings.

[0027] As shown in the figure: Figures 1-7 A fiber-optic temperature sensing device and method based on thermally coupled energy levels according to an embodiment of the present application, which comprises an excitation assembly, a sensing assembly, and a detection assembly.

[0028] It can be understood that the core of the excitation assembly is an excitation light source 1 capable of emitting 980 nm infrared light, and the output light path of the light source is directly aligned with the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 in the sensing assembly, ensuring that the emitted 980 nm infrared light can efficiently irradiate the surface of the material 2, providing excitation energy for the material.

[0029] In the sensing assembly, the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is tightly fixed to the outer wall of the temperature control device 3 (such as the outer wall of the conical flask of a constant-temperature magnetic stirrer) by special resin glue, which can ensure the thermal conductivity efficiency between the material 2 and the temperature control device 3, so that the temperature of the material 2 can change synchronously with the temperature of the temperature control device 3, avoiding measurement errors caused by thermal hysteresis.

[0030] The detection assembly includes an optical fiber 4 and a spectrometer 5, wherein the input end of the optical fiber 4 is close to the surface of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 (forms a reasonable angle with the irradiation direction of the excitation light source 1 to avoid direct interference of the excitation light with the fluorescence signal), and the output end is connected with the signal input end of the spectrometer 5, for stably transmitting the fluorescence signal generated by the material 2 to the spectrometer 5.

[0031] Workflow: After the device is started, the excitation light source 1 first emits 980 nm infrared light, which is directly irradiated on the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 of the sensing assembly. Through the strong absorption of Yb3+ ions to 980 nm light and energy transfer in the material, the Er3+ ions are excited to occur energy level transition, and then characteristic fluorescence is generated.

[0032] At the same time, the temperature control device 3 changes the temperature of its outer wall through its temperature control function. Since the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is fixed on the outer wall of the temperature control device 3 by special resin glue, the temperature of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 changes synchronously with the temperature of the temperature control device 3, so as to ensure that the temperature environment of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is consistent with the temperature to be measured.

[0033] The fluorescence signal (mainly from the 2H 11 / 2 and 4 S3 / 2 energy level transition of Er3+) generated by the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 under excitation is captured by the input end of the optical fiber 4 of the detection assembly. Through the low-loss transmission characteristics of the optical fiber 4, the fluorescence signal is efficiently conducted to the spectrometer 5, and the fluorescence spectrum is collected and preliminarily analyzed by the spectrometer 5, which lays a foundation for subsequent calculation of temperature by fluorescence intensity ratio.

[0034] Through the above structural design, the excitation assembly, the sensing assembly and the detection assembly form a complete optical path and temperature control closed loop: the excitation light source 1 provides energy input, the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 of the sensing assembly serves as a temperature sensitive unit to convert temperature information into fluorescence characteristic change, and the detection assembly is responsible for the collection and transmission of the fluorescence signal, so as to realize the basic function of temperature sensing in cooperation. Among them, the synchronous temperature control design (fixed by special resin glue) of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 and the temperature control device 3 is the key to ensure the measurement accuracy, which can effectively avoid the signal distortion caused by the temperature difference between the material and the temperature control device.

[0035] In an embodiment of the present application, as shown in Figures 1-7 , the temperature control device 3 is a constant temperature magnetic stirrer, and the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is fixed on the outer wall of the conical flask of the constant temperature magnetic stirrer.

[0036] It can be understood that in the device, the temperature control device 3 specifically adopts a constant temperature magnetic stirrer (model LKTC-B2-T, Tianjin Sailight Experimental Analysis Instrument Manufacturing Plant), which has a stable temperature control function, can realize accurate temperature control in the range of 313-363K (40-90℃), the temperature control accuracy is ±0.5K, and can provide a stable temperature environment for the sensing process. The core working parts of the constant temperature magnetic stirrer include a heating base and a placeable conical flask. The conical flask is used as a temperature conduction carrier, and the outer wall material of the conical flask is high-temperature-resistant glass, which has good heat conductivity and can uniformly transmit the temperature of the heating base to the surface of the bottle body.

[0037] The YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is fixed on the outer wall of the conical flask of the constant temperature magnetic stirrer by special resin glue. The specific fixing process is as follows: a proper amount of YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is mixed with special resin glue at a mass ratio of 1:2, and after being stirred into a uniform paste, it is uniformly applied to the specified area (an area of about 1 cm2) on the outer wall of the conical flask by a cotton swab, the thickness of the application is controlled to be 0.5-1 mm, and then the glue is cured at room temperature for 2 hours. The reason for using special resin glue is that it not only has good bonding strength (the peel strength after curing is ≥5N / cm), but also has excellent heat conduction performance (thermal conductivity ≥0.8W / (m·K)), which can ensure that the temperature of the outer wall of the conical flask is efficiently transmitted to the YVO4:Yb3+ / Er3+ co-doped luminescent material 2, so that the temperature of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is synchronized with the temperature of the outer wall of the conical flask (the temperature difference is ≤0.3K), and the temperature lag caused by excessive thermal resistance is avoided.

[0038] When working, the constant temperature magnetic stirrer heats the conical flask through the heating base, and after the conical flask absorbs heat, the temperature of the outer wall changes with the temperature of the heating base; since the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is closely attached to the outer wall of the conical flask by special resin glue, the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 quickly responds to the temperature change of the outer wall of the conical flask through heat conduction, and realizes the synchronous rise and fall with the temperature of the conical flask. The core advantage of this design is that: by means of the stable temperature control ability of the constant temperature magnetic stirrer and the uniform heat conduction characteristics of the conical flask, combined with the efficient heat transfer effect of the special resin glue, it is ensured that the temperature environment of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is consistent with the target temperature set by the constant temperature magnetic stirrer, which provides an accurate temperature reference for subsequent temperature sensing based on the change of the fluorescence characteristics of the material, and avoids the measurement error caused by the temperature difference between the material and the temperature control device.

[0039] In an embodiment of the present application, as Figures 1-7As shown, the doping concentration of Er³⁺ in the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is 1%-5%.

[0040] It can be understood that the doping concentration of Er³⁺ in the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is 1%-5%, and the "doping concentration" here refers to the mole percentage of Er³⁺ ions occupying Y³⁺ ion sites in the YVO4 crystal, that is, 1-5 mol of Er³⁺ ions are substituted for every 100 mol of Y³⁺ ions, and the remaining 95-99 mol is still Y³⁺ ions.

[0041] In the material preparation process, the concentration range is accurately controlled by weighing the raw materials: according to the stoichiometric ratio of YVO4, when the yttrium-containing compound (such as Y2O3) and the erbium-containing compound (such as Er2O3) are weighed, the molar ratio of Er2O3 to Y2O3 is ensured to meet 1%-5% of Er³⁺ occupying Y³⁺ sites. For example, if 1 mol of YVO4 substrate is prepared, when the Er³⁺ doping concentration is 1%, 0.99 mol of Y2O3 and 0.01 mol of Er2O3 (to provide 0.02 mol of Er³⁺, corresponding to 1% site substitution) need to be weighed; when the concentration is 5%, 0.95 mol of Y2O3 and 0.05 mol of Er2O3 are weighed, and the rest of the raw materials (vanadium-containing compound, ytterbium-containing compound) are weighed in corresponding proportions, and after mixing, YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is prepared by high-temperature solid phase method.

[0042] The range of 1%-5% is selected as the doping concentration of Er³⁺ based on the following technical considerations: If the doping concentration of Er³⁺ is less than 1%, the number of Er³⁺ ions in the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is too small, and after being excited by 980 nm laser, the fluorescence signal intensity generated by the ²H 11 / 2 and 4 S3 / 2 energy levels is weak, resulting in a decrease in the signal-to-noise ratio of the fluorescence intensity ratio (FIR), affecting the temperature measurement accuracy; If the doping concentration of Er³⁺ is higher than 5%, the ion distance is too close, and non-radiative transition processes such as cross-relaxation are prone to occur (i.e. concentration quenching), resulting in a decrease in fluorescence quantum yield, and the change rule of the fluorescence intensity ratio of the ²H 11 / 2 and 4 S3 / 2 energy levels with temperature deviates from the Boltzmann distribution, destroying the linear or exponential relationship between temperature and FIR, and making it impossible to achieve stable temperature sensing.

[0043] The concentration range of 1%-5% can balance the above contradictions: in this range, the Er³⁺ ions in the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 can not only be efficiently transferred by Yb³⁺ (Yb³⁺ absorbs 980 nm light and transfers energy to Er³⁺) to produce a strong fluorescence signal, but also avoid abnormal luminescent characteristics caused by concentration quenching, thereby ensuring the fluorescence intensity ratio of 2H 11 / 2 and 4 The fluorescence intensity ratio of S3 / 2 as a function of temperature presents a stable Boltzmann distribution, which provides a reliable optical property basis for subsequent FIR temperature calculation.

[0044] In an embodiment of the present application, as shown in Figures 1-7 the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 has a doping concentration of 2% for Er³⁺ and a doping concentration of 20% for Yb³⁺.

[0045] It can be understood that in the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2, the doping concentration of Er³⁺ is 2%, and the doping concentration of Yb³⁺ is 20%. Here, the "doping concentration" refers to the mole percentage of the corresponding ion occupying the Y³⁺ ion site in the YVO4 crystal, that is, in the Y³⁺ ion site of the YVO4 matrix, 2% of the sites are replaced by Er³⁺ ions, 20% of the sites are replaced by Yb³⁺ ions, and the remaining 78% of the sites are still Y³⁺ ions. A stable YVO4:Yb³⁺ / Er³⁺ co-doped crystal structure is formed by this proportion.

[0046] In the preparation process of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2, the concentration ratio is controlled by accurate weighing of raw materials: according to the stoichiometric ratio of YVO4, when the yttrium-containing compound (such as Y2O3), the erbium-containing compound (such as Er2O3), and the ytterbium-containing compound (such as Yb2O3) are weighed, it is ensured that the mole amount of Er³⁺ ions provided by Er2O3 accounts for 2% of the total mole amount of Y³⁺, and the mole amount of Yb³⁺ ions provided by Yb2O3 accounts for 20% of the total mole amount of Y³⁺. For example, when preparing 1 mol of YVO4 matrix, 0.78 mol of Y2O3 (providing 1.56 mol of Y³⁺, accounting for 78%), 0.01 mol of Er2O3 (providing 0.02 mol of Er³⁺, accounting for 2%), and 0.1 mol of Yb2O3 (providing 0.2 mol of Yb³⁺, accounting for 20%) are weighed. Then, a vanadium-containing compound (such as V2O5) is added in proportion, ground and mixed, pre-fired (800-900°C, 4-6 hours), sintered (1000-1200°C, 6-10 hours), and post-treated, to finally obtain the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 meeting the concentration requirements.

[0047] The Er³⁺ and Yb³⁺ doping concentrations of 2% and 20% are selected based on the synergistic optimization of the luminescence performance of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 and the temperature sensing requirements: For the 2% concentration of Er³⁺: At this ratio, the Er³⁺ ions are uniformly distributed in the YVO4 crystal, which can not only ensure efficient energy transfer from Yb³⁺ (avoiding weak fluorescence signals due to low concentration) but also avoid cross relaxation (non-radiative transition) caused by too close ion distance, thereby ensuring the stability of the fluorescence emission intensity of the ²H 11 / 2 and 4 S3 / 2 energy levels, and the ratio (FIR) of the two strictly follows the Boltzmann distribution with temperature changes (the fitting goodness R²=0.997 in the experiment).

[0048] For the 20% concentration of Yb³⁺: Yb³⁺, as a sensitizer, has strong absorption ability for 980 nm infrared light (corresponding to the ²F7 / 2→²F5 / 2 energy level transition), and a concentration of 20% can maximize the absorption of 980 nm excitation light energy and efficiently transfer the energy to the ²H 4 I 11 / 2 energy level of Er³⁺ through resonant energy transfer, significantly enhancing the fluorescence emission intensity of Er³⁺ (the signal-to-noise ratio of the emission peaks at 525 nm and 550 nm is improved by more than 3 times in the experiment), providing a sufficient signal basis for accurate calculation of FIR.

[0049] At this concentration, YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 exhibits optimal sensing performance in the temperature range of 313-363 K: under 980 nm laser excitation, the ²H 11 / 2 (525 nm) and 4 S3 / 2 (550 nm) emission peaks of Er³⁺ are moderate and stable, the relative sensitivity reaches a maximum value of 0.792 at 313 K, which is more than 15% higher than other concentration combinations (such as Er³⁺ 1%+Yb³⁺ 10%), and the temperature uncertainty is ≤0.2 K, fully meeting the requirements of high-precision temperature sensing.

[0050] As shown in Figures 1-7 , the optical fiber temperature sensing method based on thermally coupled energy levels according to the embodiments of the present application prepares YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material with a specific doping ratio by a high-temperature solid-phase method, and realizes sensing by utilizing the correlation between its fluorescence characteristics and temperature. The specific steps and work flow are as follows: 1. Preparation of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 (high-temperature solid-phase method) This step synthesizes a sensing material with a specific ion doping ratio by a high-temperature solid-phase method, and the specific operation is as follows: Raw material weighing: According to the stoichiometric ratio, weigh the vanadium-containing compound (such as V2O5), ytterbium-containing compound (such as Yb2O3), erbium-containing compound (such as Er2O3), and yttrium-containing compound (such as Y2O3). The doping concentration of Er³⁺ is 1%-5% (molar percentage of Y³⁺ sites), and the doping concentration of Yb³⁺ is 10%-30% (molar percentage of Y³⁺ sites). For example, if 1 mol of YVO4 substrate is prepared, when the Er³⁺ concentration is 2% and the Yb³⁺ concentration is 20%, 0.78 mol of Y2O3, 0.01 mol of Er2O3, 0.1 mol of Yb2O3, and the corresponding molar amount of V2O5 are weighed to ensure the accurate proportion of ions.

[0051] Grinding and mixing: Put the weighed raw materials into a agate mortar and grind for 30-60 minutes until the powder is uniformly mixed. The purpose is to reduce the particle size of the raw materials and increase the contact area to provide sufficient conditions for subsequent high-temperature reaction.

[0052] Pre-burning treatment: Transfer the mixed powder to a ceramic crucible and place it in a ceramic fiber box-type electric resistance furnace (model LC-RF1-12TP). Set the pre-burning temperature to 800-900°C and keep it for 4-6 hours. Pre-burning can remove water, impurities and volatile components in the raw materials, and promote preliminary solid-phase reaction to avoid material structure defects caused by intense reaction during subsequent sintering.

[0053] Second grinding and sintering: After the pre-burning product is naturally cooled, it is taken out and ground again in an agate mortar for 20-30 minutes to fine powder. Then it is placed back into a high-temperature furnace and set to a sintering temperature of 1000-1200°C for 6-10 hours. High-temperature sintering can promote ion diffusion and form a stable YVO4 crystal structure, ensuring that Er³⁺ and Yb³⁺ are uniformly doped into the lattice to form a material with stable luminescent properties.

[0054] Post-processing: After sintering is completed, the furnace is cooled to room temperature, the product is taken out and ground again, and then washed with deionized water for 3-5 times to remove surface residual impurities. After drying, YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is obtained.

[0055] 2, Material fixation The prepared YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 was fixed to the outer wall of the temperature control device 3 using a special resin adhesive. Specifically, an appropriate amount of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 was mixed with the special resin adhesive at a mass ratio of 1:2 to form a paste. This paste was then evenly applied to the outer wall of the temperature control device 3 (the outer wall of the conical flask of the thermostatic magnetic stirrer), with a thickness controlled at 0.5-1 mm. The mixture was allowed to cure at room temperature for 2 hours. This fixing method ensures efficient heat transfer between the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 and the temperature control device 3, allowing the temperature of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 to change synchronously with the temperature of the temperature control device 3, avoiding measurement errors caused by thermal hysteresis.

[0056] 3. Activation process The fixed YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 was excited using a 980nm laser, with the excitation temperature controlled within the range of 313-363K (40-90℃). Specifically, a 980nm infrared light source was activated, allowing the laser beam to directly irradiate the surface of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2. Through the strong absorption of 980nm light by Yb³⁺ ions (corresponding to the ²F7 / 2→²F5 / 2 energy level transition of Yb³⁺), energy was transferred to Er³⁺ ions via non-radiative transitions, causing Er³⁺ ions to transition from the ground state to a higher energy level, providing the energy basis for subsequent fluorescence emission. Simultaneously, the temperature of its outer wall was adjusted by a temperature control device 3, allowing for stepwise or continuous temperature changes within the 313-363K range of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2, simulating different temperature environments to be measured.

[0057] 4. Fluorescence signal transmission and acquisition Upon excitation, the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material exhibits characteristic fluorescence as Er³⁺ ions transition from higher to lower energy levels, primarily emanating from ²H⁺ ions. 11 / 2 and 4 The emission peaks of the two thermally coupled energy levels S3 / 2 are observed. The fluorescence signal is captured and transmitted to the spectrometer 5 by placing the fiber optic cable 4 close to the surface of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 (at a 30-45° angle to the laser incident direction to avoid direct interference from the excitation light). The fiber optic cable 4 is then placed close to the surface of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 (at a 30-45° angle to the laser incident direction to avoid direct interference from the excitation light). The spectrometer 5 performs spectral dispersion and detection on the received fluorescence signal, and collects and records the ²H emission peaks. 11 / 2 and 4 Emission peak data corresponding to the S3 / 2 energy level (the center wavelengths of the two emission peaks in the experiment are located at 525nm and 550nm, respectively).

[0058] 5. Data analysis and temperature sensing implementation The emission peaks collected by spectrometer 5 are integrated to obtain the ratio of the integrated intensities of the two emission peaks, i.e., the fluorescence intensity ratio (FIR). Since ²H 11 / 2 and 4 S3 / 2 is a thermally coupled energy level, and its particle population follows a Boltzmann distribution. Therefore, the FIR (Fluid-Induced Reduction) varies with temperature in a definite functional relationship. Fitting the FIR values ​​at different temperatures yields a distribution curve conforming to FIR = Bexp(-C / T) (where B is the fitting parameter, C is a constant related to the energy level difference, and T is the temperature) (the goodness of fit R² = 0.997 in the experiment). Based on this fitted curve, the corresponding temperature can be obtained by measuring the FIR value at an unknown temperature, thus achieving temperature sensing.

[0059] The above steps, through a complete process of "material preparation-fixation-excitation-signal acquisition-analysis", utilize the thermal coupling energy level characteristics of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 to convert temperature information into a measurable fluorescence intensity ratio signal, ultimately achieving temperature sensing in the range of 313-363K. Moreover, the method achieves a relative sensitivity of 0.792 at 313K and a temperature uncertainty ≤0.2K, meeting the requirements for high-precision temperature measurement.

[0060] In one embodiment of this application, such as Figures 1-7 As shown, in the fiber optic temperature sensing method based on thermally coupled energy levels, the step "acquiring the two main emission energy levels of Er³⁺ (²H)" is described. 11 / 2 and 4 In the emission peak of S3 / 2), the center wavelengths of the emission peaks of the two energy levels are located at 525nm and 550nm, respectively. The formation mechanism and its role in the sensing method are as follows: 1. Sources and characteristics of emission peaks When the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is excited by a 980nm laser, the Yb³⁺ ions absorb the 980nm photon and transition from the ²F7 / 2 energy level to the ²F5 / 2 energy level. Subsequently, they transfer energy to the Er³⁺ ions through energy transfer, causing the Er³⁺ ions to transition from the ground state. 4 I 15 / 2 jump to 4 I 11 / 2 energy level; some Er³⁺ ions further absorb energy and transition to the / 2 energy level. 4 The F7 / 2 energy level is then populated to ²H via nonradiative transitions. 11 / 2 and 4 S3 / 2 energy level. When Er³⁺ ions move from²H⁺ 11 / 2 energy level transition to ground state 4 I 15 When / 2, the released energy corresponds to fluorescence emission at a wavelength of 525nm; from 4The S3 / 2 energy level transitions to the ground state. 4 I 15 At / 2, the released energy corresponds to fluorescence emission at a wavelength of 550 nm. These two wavelengths represent the energy released when Er³⁺ ions are in a YVO₄ crystal field environment, with ²H⁺ ions emitting fluorescence at a wavelength of 550 nm. 11 / 2→ 4 I 15 / 2 and 4 S3 / 2→ 4 I 15 The characteristic emission wavelength of the / 2 transition exhibits stability and specificity—in the experiment, within the temperature range of 313-363K, the center wavelength deviation between the two emission peaks was less than 2nm, ensuring the consistency of signal acquisition.

[0061] 2. Workflow in the sensing method When the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is excited by a 980nm laser, the resulting fluorescence signal, containing wavelengths of 525nm and 550nm, is transmitted to a spectrometer 5 via optical fiber 4. The spectrometer 5 performs spectral processing on the fluorescence signal, and through wavelength scanning, it can clearly identify and record the center wavelength of 525nm (corresponding to ²H₂O₄). 11 / 2 energy level) and 550nm (corresponding to 4 The emission peaks of the S3 / 2 energy level. Since these two emission peaks originate from a pair of thermally coupled energy levels of Er³⁺, their intensity is significantly affected by temperature and the change law is clear—as the temperature increases, ²H 11 The particle population of the / 2 energy level increases according to the Boltzmann distribution law, and the intensity of the 525nm emission peak is relatively enhanced. 4 The particle population of the S3 / 2 energy level is relatively reduced, and the intensity of the 550nm emission peak is relatively weakened. The intensity ratio (FIR) of the two shows a stable relationship with temperature.

[0062] 3. The necessity of choosing this wavelength 525nm and 550nm as ²H 11 / 2 and 4 The characteristic emission wavelength of the S3 / 2 energy level has the following advantages: High signal strength: The signal-to-noise ratio of the fluorescence emission peaks at both wavelengths in the experiment was greater than 30dB, which ensured the accuracy of the integral calculation; Good spectral separation: The center wavelengths of the two peaks differ by 25nm, with no obvious overlap. The spectrometer 5 can clearly distinguish and integrate them separately, avoiding signal interference. Stable temperature response: In the range of 313-363K, the emission peak intensity ratio (FIR) of the two wavelengths strictly follows the Boltzmann distribution with temperature, and the goodness of fit R²=0.997, providing reliable characteristic parameters for temperature inversion.

[0063] Therefore, collecting emission peaks at 525 nm and 550 nm is the core step in calculating fluorescence intensity ratio (FIR) and realizing temperature sensing. Its stability and specificity directly guarantee the accuracy and reliability of the sensing method.

[0064] In one embodiment of this application, such as Figures 1-7 As shown, in the step "fitting the fluorescence intensity ratio as a function of temperature, with the fit satisfying a Boltzmann distribution", the fitting formula for the fluorescence intensity ratio (FIR) is FIR = Bexp(-C / T), where B is the fitting parameter, C is a constant related to the energy difference between the two energy levels, and T is the temperature. The origin of this formula, the meaning of the parameters, and its role in the sensing process are as follows: 1. Physical basis of the formula Fluorescence intensity ratio (FIR) refers to the ratio of the two principal emission levels of Er³⁺ (²H⁺). 11 / 2 and 4 The ratio of the integrated emission peak intensity corresponding to S3 / 2 (i.e., the ratio of the integrated emission peak intensity at 525 nm to the integrated emission peak intensity at 550 nm). Since ²H 11 / 2 and 4 S3 / 2 is a thermally coupled energy level (energy difference approximately 778 cm⁻¹), and its particle population follows the Boltzmann distribution law: under thermal equilibrium, the higher energy level (²H) 11 / 2) and low energy level ( 4 The ratio of the number of particles in S3 / 2 is exponentially related to temperature. Since fluorescence intensity is directly proportional to the particle population, the change in FIR with temperature can be expressed as the exponential form FIR = Bexp(-C / T), where: T is absolute temperature (unit: K); C is a constant related to the energy difference (ΔE) between the two energy levels, satisfying C=ΔE / k (k is the Boltzmann constant); B is the fitting parameter, which is related to factors such as the transition probability of the two energy levels and the fluorescence quantum yield.

[0065] 2. Fitting process and parameter determination In the experiment, the temperature of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 was stabilized at multiple discrete points (e.g., 313K, 323K, ..., 363K) within the range of 313-363K using a temperature control device 3. At each temperature point, the fluorescence signal was transmitted to a spectrometer 5 via an optical fiber 4, and the fluorescence signal was collected. 11 / 2 and 4 The emission peak of the S3 / 2 energy level is calculated and the integrated intensity is obtained to obtain the FIR value at the corresponding temperature. Substituting multiple sets of (temperature T, FIR) data into the formula FIR=Bexp(-C / T), the values ​​of parameters B and C can be determined by fitting the data using the least squares method.

[0066] For example, after fitting the measurement data of YVO4:2%Er³⁺,20%Yb³⁺ co-doped luminescent material 2 in the experiment, the formula FIR=8.49exp(-778 / T) was obtained, where B=8.49 (fitting parameter) and C=778 (with ²H 11 / 2 and 4 The energy level difference of S3 / 2 is related to the energy level difference ΔE = 778 × k × T / T = 778 cm⁻¹), and the goodness of fit R² = 0.997, indicating that the formula can accurately describe the relationship between FIR and temperature.

[0067] 3. Its role in temperature sensing This fitting formula is the core mathematical model for achieving temperature sensing. In actual temperature measurement, for an environment with an unknown temperature, the fluorescence signal of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is collected via optical fiber 4, and the result is obtained via spectrometer 5. 11 / 2 and 4 The integral intensity of the emission peak of the S3 / 2 energy level is used to calculate the FIR value. Then, the FIR value is substituted into the fitting formula FIR=Bexp(-C / T) to obtain the temperature T (i.e., T=-C / ln(FIR / B)).

[0068] Since the formula is derived based on the Boltzmann distribution and has high experimental fitting accuracy (R²=0.997), it can ensure the accuracy of temperature measurement. Experimental verification shows that in the range of 313-363K, the deviation between the temperature obtained by using this formula and the actual temperature is ≤0.2K, which meets the requirements of high-precision sensing.

[0069] In summary, the fitting formula FIR=Bexp(-C / T) is the key bridge connecting fluorescence signal and temperature. Its parameters are determined by fitting experimental data. Based on the particle population law of thermally coupled energy levels, it provides a reliable mathematical basis for accurate temperature inversion and is the core step of this sensing method to achieve temperature measurement.

[0070] In one embodiment of this application, such as Figures 1-7 As shown, the step involves "the relative sensitivity of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 at 313K is 0.792". Here, "relative sensitivity" is a core indicator for evaluating temperature sensing performance, defined as the relative change rate of fluorescence intensity ratio (FIR) with temperature. The specific calculation is based on the fitting relationship between fluorescence intensity ratio and temperature. The acquisition and significance of this value are as follows: 1. Definition and calculation basis of relative sensitivity The formula for calculating relative sensitivity (Sr) is: Sr = (1 / FIR) × (dFIR / dT), where FIR is the fluorescence intensity ratio (²H). 11 / 2 energy level emission peak integral intensity and4 The ratio of the integrated intensity of the emission peak of the S3 / 2 energy level), T is the temperature (unit: K), and dFIR / dT is the derivative of FIR with respect to temperature. The physical meaning of this formula is: the relative change in FIR caused by a unit change in temperature; the larger the value, the more sensitive the material is to temperature.

[0071] In this method, since the relationship between FIR and temperature satisfies the fitting formula FIR=Bexp(-C / T) (where B is the fitting parameter and C is a constant related to the energy level difference), differentiating this formula yields dFIR / dT=Bexp(-C / T)×(C / T²)=FIR×(C / T²). Substituting this into the relative sensitivity formula and simplifying, we get Sr=C / T², meaning the relative sensitivity is only related to the constant C and the temperature T, where C is determined by Er³⁺²H. 11 / 2 and 4 The energy level difference of S3 / 2 is determined (in the experiment, the fitting yielded C=778).

[0072] 2. Procedure for obtaining a relative sensitivity of 0.792 at 313K The steps for measuring and calculating the relative sensitivity of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 at 313K are as follows: First, the temperature of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is stabilized at 313K using temperature control device 3. Then, the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 is excited using a 980nm laser to generate luminescent material containing ²H. 11 / 2 and 4 Fluorescence signal of the emission peak of the S3 / 2 energy level; The fluorescence signal is transmitted to spectrometer 5 via optical fiber 4, and spectrometer 5 collects and records the fluorescence signal at 525 nm (²H). 11 / 2 energy level) and 550nm ( 4 The emission peak at the S3 / 2 energy level was used to calculate the FIR value at that temperature through integration. Keeping other conditions constant, make small adjustments to the temperature around 313K (e.g., 312K, 313K, 314K), repeat the above steps to obtain the FIR value at the corresponding temperature, and calculate the rate of change of FIR with temperature dFIR / dT. Substituting the FIR value at 313K and dFIR / dT into the relative sensitivity formula Sr=(1 / FIR)×(dFIR / dT), and combining it with the FIR-temperature fitting formula (FIR=Bexp(-C / T)) to derive Sr=C / T², and substituting C=778 and T=313K, we calculate Sr=778 / (313²)≈0.792, which is consistent with the experimental measurement results.

[0073] 3. The technical significance of this value The relative sensitivity at 313K is 0.792, indicating that at this temperature, the relative change in fluorescence intensity ratio (FIR) of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is 0.792% per 1K change in temperature, which is significantly higher than the relative sensitivity of traditional thermally coupled level temperature measurement materials in the same temperature range (experimental data show an increase of 1.36 times compared to traditional materials). This result reflects the high sensitivity of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 in the low temperature range (near 313K) - since the higher the relative sensitivity, the stronger the resolution of small temperature changes, therefore this material has a significant advantage in low-temperature high-precision temperature measurement scenarios (such as precise instrument temperature control, local biological tissue temperature measurement).

[0074] In summary, the relative sensitivity of 0.792 of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 at 313K is a key performance indicator derived from experimental measurement of the change in FIR with temperature and fitting formula, directly reflecting the sensitivity of the material as a temperature sensing medium, and is the core embodiment of the high-precision characteristics of the sensing method of the present application.

[0075] In an embodiment of the present application, as shown in Figures 1-7 The step of "controlling the temperature at 313-363K by the temperature control device 3" is a key operation to achieve stable temperature sensing, and its specific implementation, temperature range selection basis and working process are as follows: 1. Operation and temperature control principle of the temperature control device 3 The temperature control device 3 is a constant temperature magnetic stirrer (model LKTC-B2-T, Tianjin Saidelesi Experimental Analysis Instrument Manufacturing Plant), which has precise temperature adjustment function, can set the target temperature through the control panel and display the current temperature in real time, and the temperature control accuracy is ±0.5K. The device heats the conical flask placed on the heating base through the heating base, and the temperature of the outer wall of the conical flask changes synchronously with the temperature of the heating base; and the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is fixed on the outer wall of the conical flask by special resin glue, and the glue has good thermal conductivity (thermal conductivity ≥0.8W / (m·K)), so that the temperature of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 can be consistent with the temperature of the outer wall of the conical flask (temperature difference ≤0.3K), so that the temperature of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 can be accurately controlled in the range of 313-363K.

[0076] 2. Setting and working process of 313-363K temperature range In the experiment, the specific operation process of controlling the temperature at 313-363K (i.e. 40℃-90℃, because 0℃=273.15K) by the temperature control device 3 is as follows: Start the constant temperature magnetic stirrer, set the initial temperature to 313K through its "SET" key, and wait for the device to display temperature stability (fluctuation ≤0.5K) before maintaining the temperature for 10 minutes to ensure that the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 and the outer wall of the conical flask are in thermal equilibrium, and the temperature of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is stable at 313K; After completing the fluorescence signal collection at 313K, gradually increase the temperature (10K each time, i.e. 323K, 333K, …, 363K) through the "SET" key, and maintain each temperature point for 10 minutes to achieve thermal equilibrium before collecting signals at the corresponding temperature; During the entire process, the heating base of the temperature control device 3 monitors the temperature in real time through the built-in sensor, and if it deviates from the set value, it will automatically adjust the heating power to maintain temperature stability, ensuring that the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is always within the target temperature range of 313-363K.

[0077] 3. Technical basis for selecting the range of 313-363K The determination of this temperature range is based on the fluorescence characteristics of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 and the sensing requirements: In the range of 313-363K, the 2H 11 / 2 and 4 The particle population of the S3 / 2 thermal coupling energy level of Er3+ in YVO4:Yb3+ / Er3+ co-doped luminescent material 2 strictly follows the Boltzmann distribution, and the fluorescence intensity ratio (FIR) changes with temperature in a stable exponential relationship (the fitting formula FIR=Bexp(-C / T) has a fitting goodness R2=0.997), which can realize accurate temperature inversion; Experimental verification shows that the fluorescence signal intensity of YVO4:Yb3+ / Er3+ co-doped luminescent material 2 in this range is moderate (signal-to-noise ratio ≥30dB), without obvious fluorescence quenching phenomenon, and the relative sensitivity reaches a maximum value of 0.792 at 313K, although it gradually decreases with increasing temperature, it still maintains a high level (0.582 at 363K), which can meet the high-precision sensing requirements; This range covers the industrial normal temperature and the related interval of biological body temperature (such as 40-90℃), and has practical application value, and the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 has good linearity in this interval, and the temperature uncertainty is ≤0.2K, and the measurement accuracy is better than that of traditional infrared temperature measurement technology.

[0078] In summary, the temperature is controlled at 313-363 K by the temperature control device 3, which is a necessary condition for ensuring the stability of the fluorescence characteristics of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 and realizing high-precision temperature sensing. The operation process is ensured by the precise temperature control and thermal equilibrium of the device, which ensures the consistency of the material temperature and the set temperature, and provides a reliable temperature reference for subsequent fluorescence signal analysis and temperature inversion.

[0079] In one embodiment of the present application, as shown in Figure 3 the step of "preparing the YVO4:Yb3+ / Er3+ co-doped luminescent material 2", the Er3+ doping concentration of the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 is 2%, and the Yb3+ doping concentration is 20%. Here, "doping concentration" refers to the molar percentage of the corresponding rare earth ion occupying Y3+ ion sites in YVO4 crystal, i.e., in the crystal structure of the YVO4 matrix, for every 100 mol of Y3+ ion sites, 2 mol are replaced by Er3+ ions, 20 mol are replaced by Yb3+ ions, and the remaining 78 mol are still Y3+ ions, forming a stable co-doped crystal structure through this ratio. The specific preparation control process and concentration selection basis are as follows: 1. Precise concentration control process In the process of preparing the YVO4:Yb3+ / Er3+ co-doped luminescent material 2 by the high-temperature solid-phase method, the concentrations of 2% Er3+ and 20% Yb3+ are strictly controlled through the raw material weighing and mixing steps: Raw material selection: Use yttrium-containing compounds (such as Y2O3), erbium-containing compounds (such as Er2O3), ytterbium-containing compounds (such as Yb2O3), and vanadium-containing compounds (such as V2O5) as raw materials, where Y2O3 provides Y3+, Er2O3 provides Er3+, Yb2O3 provides Yb3+, and V2O5 provides V 5 ⁺ to form the YVO4 matrix.

[0080] Weighing calculation: Taking the preparation of 1 mol of YVO4 matrix as an example, the total molar amount of Y3+, Er3+, and Yb3+ needs to be 1 mol (because the stoichiometric ratio of YVO4 is 1:1:4). Among them, Er3+ accounts for 2%, i.e., 0.02 mol, and 0.01 mol of Er2O3 (1 mol of Er2O3 provides 2 mol of Er3+) needs to be weighed; Yb3+ accounts for 20%, i.e., 0.2 mol, and 0.1 mol of Yb2O3 (1 mol of Yb2O3 provides 2 mol of Yb3+) needs to be weighed; the remaining Y3+ is 0.78 mol, and 0.39 mol of Y2O3 (1 mol of Y2O3 provides 2 mol of Y3+) needs to be weighed; the vanadium-containing compound is weighed according to the ratio of V to Y group ions (Y3++ Er3++ Yb3+) 1:1, i.e., 1 mol of V2O5.

[0081] Mix evenly: Put the above-mentioned weighed raw materials together into an agate mortar, grind for 30-60 minutes until the powder particles are uniform (particle size ≤5 μm), and ensure that each ion is in sufficient contact before the solid-phase reaction, laying a foundation for uniform doping during subsequent high-temperature sintering.

[0082] 2. Technical basis for the concentration ratio The selection of 2% Er³⁺ and 20% Yb³⁺ doping concentrations is based on the synergistic optimization of the luminescent efficiency and temperature sensing performance of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2, and the specific basis is as follows: When the Er³⁺ concentration is 2%: it can ensure that there are enough Er³⁺ ions in YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 to produce a detectable fluorescence signal (to avoid weak signal caused by too low concentration), and can avoid cross relaxation (non-radiative transition) caused by too close ion distance. Experiments show that at this concentration, the fluorescence emission intensity of Er³⁺ ²H 11 / 2 and 4 S3 / 2 energy level is stable, there is no obvious quenching, and the fluorescence intensity ratio (FIR) of the two changes clearly with temperature.

[0083] When the Yb³⁺ concentration is 20%: Yb³⁺ as a sensitizer has strong absorption ability to 980 nm infrared light (corresponding to Yb³⁺ ²F7 / 2→²F5 / 2 energy level transition), and a concentration of 20% can maximize the absorption of excitation light energy and efficiently transfer it to Er³⁺ through resonant energy transfer (Yb³⁺ ²F5 / 2 energy level matches Er³⁺ I 4 I 11 / 2 energy level), making the fluorescence intensity of Er³⁺ increase by more than 3 times compared to low concentration Yb³⁺, providing high signal-to-noise ratio signals for accurate FIR calculation.

[0084] Synergistic effect: At this concentration ratio, the fluorescence intensity ratio (FIR) of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 in the temperature range of 313-363 K has a fitting degree of R²=0.997 (satisfying the Boltzmann distribution), the relative sensitivity at 313 K is 0.792, and the temperature uncertainty is ≤0.2 K, which is better than other concentration combinations (such as Er³⁺ 1%+Yb³⁺ 10% or Er³⁺ 5%+Yb³⁺ 30%).

[0085] In summary, the control of Er³⁺ doping concentration at 2% and Yb³⁺ doping concentration at 20% in the step "preparing YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2" is a key process parameter achieved by accurately weighing the raw materials. This ratio ensures that YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material 2 has excellent fluorescence characteristics and temperature sensing performance, and is the core basis for achieving high-precision temperature measurement in this method.

[0086] Experimental Results and Analysis: like Figure 4 As shown, YVO4:2%Er under 980 nm laser excitation 3+ 20Yb 3+ The emission spectrum of phosphors changes significantly at different temperatures.

[0087] First of all, Er 3+ The two main emission levels ( 2 H 11 / 2 and 4 S 3 / 2 Both exhibited significant luminescence, with center wavelengths at 525 nm and 550 nm, respectively.

[0088] Secondly, as the temperature increases (from 323K to 363K). 4 S 3 / 2 The emission peak decreases continuously with increasing temperature, but 2 H 11 / 2 The emission peak first decreases and then increases with increasing temperature.

[0089] Finally, the two thermally coupled energy levels observed in the experiment showed strong luminescence intensity, while other emission peaks showed almost no significant luminescence. Theoretically, a higher signal-to-noise ratio could be obtained by performing fluorescence intensity ratio analysis.

[0090] like FIR As shown, YVO4:2%Er under 980 nm laser excitation 3+ 20Yb 3+ Er was collected by phosphor at different temperatures (313-363K). 3+ The two main emission levels ( 2 H 11 / 2 and 4 S 3 / 2 The launch peak of ).

[0091] First, regarding Er 3+ The two main emission levels ( 2 H 11 / 2 and 4 S 3 / 2 The fluorescence intensity ratio (FIR) was obtained by integral calculation of the emission peak of the emission peak as a function of temperature.

[0092] Secondly, a single e-exponential fit was performed on the fluorescence intensity ratio as shown in the formula, and it was found that these points satisfy the Boltzmann distribution law very well.

[0093] Figure 5 Finally, the fitting results show that the fluorescence intensity ratio is in good agreement with the fitting precision R 2 = 0.997, and the fitting parameter 778 is a constant related to the energy level difference of the two energy levels.

[0094] As Figure 6 shown, under the excitation of 980 nm laser, the YVO4:2%Er 3+ 20Yb 3+ phosphor has a significant increase in absolute sensitivity with the increase of temperature.

[0095] The absolute sensitivity of the obtained results was calculated using the following formula, and the calculation formula of the absolute sensitivity Sa is as follows: Where R represents the fluorescence intensity ratio at the same temperature, and T represents the temperature. The absolute sensitivity is the lowest at 313 K, S a-min = 0.703@313K, S a-max = 1.006@363K.

[0096] This result shows that the fluorescence intensity ratio temperature measurement has excellent temperature sensing properties in the range of 313-363 K.

[0097] Compared with the absolute sensitivity, the relative sensitivity can more accurately represent the temperature sensing sensitivity, as Figure 7 shown, under the excitation of 980 nm laser, the YVO4:2%Er 3+ 20Yb 3+ phosphor has a significant decrease in relative sensitivity with the increase of temperature.

[0098] The relative sensitivity of the obtained results was calculated using the following formula, and the calculation formula of the absolute sensitivity Sr is as follows: Where R represents the fluorescence intensity ratio at the same temperature, and T represents the temperature. The absolute sensitivity is the lowest at 313 K, S R-max = 0.792@ 313 K, S a-min = 0.582@ 363 K.

[0099] This result shows that the relative sensitivity of the fluorescence intensity ratio temperature measurement decreases with the increase of temperature in the range of 313-363 K.

[0100] As ​ shown, the temperature uncertainty is the most intuitive representation of the uncertainty of the measurement parameter.

[0101] The temperature uncertainty of the obtained results was calculated using the following formula: wherein, R represents the variation of R values obtained by multiple measurements In this experiment, we use the data obtained by ten repeated measurements R = R max -R min After multiple average value calculations R is approximately equal to 0.01.

[0102] This result shows that in the temperature range of 313-363 K, the temperature uncertainty of the high-frequency fluorescence intensity ratio measurement increases with temperature, but the overall temperature uncertainty is within 0.2 K, which is better than the current infrared temperature measurement accuracy of 1 K.

[0103] Experimental materials and instrument parameters: Table 1: Instruments used in this experiment It should be noted that the control method of the present application can be automatically controlled by a controller, and the control method of the controller can be realized by simple programming by a person skilled in the art, which belongs to the common knowledge in the art, and the present application mainly protects the mechanical structure, so the control method and circuit connection of the present application will not be explained in detail.

[0104] In summary, the optical fiber temperature sensing device and method based on thermal coupling energy level of the embodiments of the present application significantly improve the temperature sensing performance in the temperature range of 313-363 K by optimizing the doping ratio, fixing method and signal analysis method of YVO4:Yb3+ / Er3+ material, especially in the low temperature range. The relative sensitivity and measurement accuracy are excellent, and can be widely applied to high-precision temperature monitoring in the fields of precision manufacturing, biological medicine, etc.

Claims

1. A fiber optic temperature sensing device based on thermally coupled energy levels, characterized in that, It includes excitation components, sensing components, and detection components, among which, The excitation assembly includes an excitation light source (1) capable of emitting 980nm infrared light, used to excite the sensing material; The sensing component includes a YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) and a temperature control device (3). The YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is fixed to the outer wall of the temperature control device (3) with a special resin glue so that the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) can change its temperature synchronously with the temperature change of the temperature control device (3). The detection component includes an optical fiber (4) and a spectrometer (5). One end of the optical fiber (4) is used to receive the fluorescence signal generated after the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is excited, and the other end is connected to the spectrometer (5) to transmit the fluorescence signal to the spectrometer (5) for detection and analysis.

2. The fiber optic temperature sensing device based on thermally coupled energy levels according to claim 1, characterized in that, The temperature control device (3) is a thermostatic magnetic stirrer, and the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is fixed on the outer wall of the conical flask of the thermostatic magnetic stirrer.

3. The fiber optic temperature sensing device based on thermally coupled energy levels according to claim 1, characterized in that, In the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2), the doping concentration of Er³⁺ is 1%-5%.

4. The fiber optic temperature sensing device based on thermally coupled energy levels according to claim 1, characterized in that, In the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2), the doping concentration of Er³⁺ is 2% and the doping concentration of Yb³⁺ is 20%.

5. A fiber optic temperature sensing method based on thermally coupled energy levels, characterized in that, Includes the following steps: The preparation of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent materials (2) was carried out using a high-temperature solid-state method, specifically including: Weigh out vanadium-containing compounds, ytterbium-containing compounds, erbium-containing compounds, and yttrium-containing compounds in proportion, wherein the doping concentration of Er³⁺ is 1%-5% and the doping concentration of Yb³⁺ is 10%-30%; Grind and mix the raw materials in an agate mortar until they are evenly mixed. The mixed raw materials are placed in a high-temperature furnace for pre-firing at a temperature of 800-900℃ for 4-6 hours. Take out the pre-calcined product, grind it again, and then put it into a high-temperature furnace for sintering at a temperature of 1000-1200℃ for 6-10 hours. After cooling, post-processing was performed to obtain YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2); The YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is fixed to the outer wall of the temperature control device (3) using a special resin adhesive; The YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) was excited using a 980nm laser at a temperature range of 313-363K. The fluorescence signal generated by the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is transmitted to the spectrometer (5) via optical fiber (4) to collect the two main emission levels of Er³⁺ (²H). 11 / 2 and 4 The emission peak of S3 / 2); The emission peak is integrated to obtain the fluorescence intensity ratio (FIR), and the change of the fluorescence intensity ratio with temperature is fitted. The fit satisfies the Boltzmann distribution, and temperature sensing is realized based on this.

6. The fiber optic temperature sensing method based on thermally coupled energy levels according to claim 5, characterized in that, In the step, the two main emission levels of Er³⁺ (²H) 11 / 2 and 4 The center wavelengths of S3 / 2 are located at 525nm and 550nm, respectively.

7. The fiber optic temperature sensing method based on thermally coupled energy levels according to claim 5, characterized in that, In this step, the fitting formula for the fluorescence intensity ratio (FIR) is FIR=Bexp(-C / T), where B is the fitting parameter, C is a constant related to the energy difference between the two energy levels, and T is the temperature.

8. The fiber optic temperature sensing method based on thermally coupled energy levels according to claim 5, characterized in that, The relative sensitivity of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) at 313 K is 0.

792.

9. The fiber optic temperature sensing method based on thermally coupled energy levels according to claim 5, characterized in that, In this step, the temperature is controlled at 313-363K by the temperature control device (3).

10. The fiber optic temperature sensing method based on thermally coupled energy levels according to claim 5, characterized in that, In step "Preparation of YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2)", the Er³⁺ doping concentration of the YVO4:Yb³⁺ / Er³⁺ co-doped luminescent material (2) is 2%, and the Yb³⁺ doping concentration is 20%.

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