CN116656355B - Red fluorescent material and optical temperature measurement application and application method thereof - Google Patents

Abstract

The present invention provides a red fluorescent material, which uses NaNH ₄ TaF ₇ as a matrix and Mn ⁴⁺ as an activator, and has a chemical composition of Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ , 0.5%≤x≤10%. The red fluorescent material can be excited by ultraviolet or blue light, and emits narrow-band red light of 580-680nm, with the strongest wavelength at 628.8nm. The luminous intensity of the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ will change significantly with the change of temperature. By utilizing this temperature-dependent characteristic, the red fluorescent material can be applied to optical temperature measurement, and the red fluorescent material has the characteristics of fast response speed, high temperature measurement sensitivity and wide temperature measurement range, and has a high application prospect in optical temperature measurement.

Description

A red fluorescent material and its optical temperature measurement application and application method

Technical Field

The present invention belongs to the field of luminescent materials, and in particular, relates to a red fluorescent material and an optical temperature measurement application and an application method thereof.

Background Art

In recent years, the process of industrial modernization in my country and the continuous high-speed growth of the electronic information industry have driven the rapid rise of the sensor market. Data show that the scale of China's sensor market in 2020 was 251 billion yuan, a year-on-year increase of 14.7%. With the increase in the demand for temperature control in industrial production, the requirements for temperature sensors are also getting higher and higher. Conventional temperature measurement based on the relationship between material properties such as volume, resistance, and magnetism and temperature has defects such as low sensitivity and long response time.

Optical temperature measurement technology uses the fluorescence characteristics of luminescent materials and combines image processing technology. It has the advantages of non-contact, high sensitivity, and fast response speed. Optical temperature measurement materials are widely used in chemical production fields represented by metallurgy and coal refining, and medical diagnosis fields such as intracellular thermal sensing.

However, most inorganic optical temperature measurement materials on the market currently use rare earth ions of ff transition or transition metal ions of dd instrument as activation ions, and their temperature measurement sensitivity is poor and the temperature measurement range is narrow. Chinese patent CN113004892A discloses a luminescent material based on cerium and europium activated aluminosilicate, the maximum absolute sensitivity of which is about 0.0188K ^-1 and the maximum relative sensitivity is about 1.35% K ^-1 , so the temperature measurement sensitivity and temperature measurement range of the luminescent material prepared by the invention still need to be further explored.

Therefore, it is necessary to develop an optical temperature measurement material with high temperature measurement sensitivity and a wide temperature measurement range.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a red fluorescent material and its optical temperature measurement application and application method, so that the red fluorescent material has the characteristics of fast response speed, high temperature measurement sensitivity and wide temperature measurement range, and can be applied to optical temperature measurement.

According to a first aspect of the present invention, a red fluorescent material is provided, with NaNH ₄ TaF ₇ as a matrix and Mn ⁴⁺ as an activator, and the chemical composition is Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ , 0.5%≤x≤10%.

The red fluorescent material provided by the present invention uses ammonium salt fluoride Na(NH ₄ )TaF ₇ as a matrix and Mn ⁴⁺ as an activator, so that Ta ⁵⁺ in the matrix can be occupied by Mn ⁴⁺ , and Mn ⁴⁺ is doped into Na(NH ₄ )TaF ₇ , and the doping amount is 0.5% to 10%. The prepared red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ has the advantages of strong luminous brightness and sensitive response of luminous intensity to temperature. Secondly, Mn ⁴⁺ ions whose outer electrons are 3d electron layers have the property of being easily affected by changes in the crystal field. When Mn ⁴⁺ acts as an activator and occupies Ta ⁵⁺ ions in a matrix with special coordination, the prepared red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ has special luminescence properties, and the luminescence intensity will change significantly with changes in temperature. That is, the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ provided by the present invention has high sensitivity to temperature changes, and the red fluorescent material has temperature-dependent characteristics within a wider temperature range. Therefore, the red fluorescent material has the characteristics of fast response speed, high temperature measurement sensitivity and wide temperature measurement range.

Preferably, the red fluorescent material is prepared by the following steps: S1. uniformly mixing a tantalum source and a hydrofluoric acid aqueous solution, and reacting them at 100-180°C for 7-24 hours to obtain a first precursor solution; S2. uniformly mixing a sodium source, an ammonium source, and deionized water with the first precursor solution, and reacting them at 100-180°C for 7-24 hours to obtain Na( _NH4 ) _TaF7 ; S3. uniformly mixing a manganese source and a hydrofluoric acid aqueous solution to obtain a second precursor solution, and then adding Na( _NH4 ) _TaF7 to the second precursor solution to partially dissolve Na( _NH4 ) _TaF7 , and adding anhydrous ethanol to the second precursor solution to recrystallize and precipitate Na( _NH4 ) _TaF7 :xMn4 ⁺ to obtain a red fluorescent material.

The present invention adopts a recrystallization method to prepare a red fluorescent material. By utilizing the different solubilities of hydrofluoric acid aqueous solution and anhydrous ethanol to ammonium heptafluorotantalate Na(NH ₄ )TaF ₇ , Na(NH ₄ )TaF ₇ and Mn ⁴⁺ dissolved in a second precursor solution can be recrystallized so that Ta ⁵⁺ in the matrix can be occupied by Mn ⁴⁺ , and Mn ⁴⁺ is doped into Na(NH ₄ )TaF ₇ , thereby preparing a red fluorescent material with high luminous brightness and luminous intensity sensitive to temperature.

Preferably, in S1, the ratio of the added molar amount of the tantalum source to the volume of the hydrofluoric acid aqueous solution is 1 to 4 mmol/mL.

When the addition amount of tantalum source and hydrofluoric acid aqueous solution meets the above conditions, the yield of Na(NH ₄ )TaF ₇ polycrystalline particles can be increased. If the ratio of the added molar amount of tantalum source to the amount of HF solution is less than 1mmol/L, it is equivalent to that the feeding amount of tantalum source is too small, which will cause the concentration of tantalum ions in the first precursor to be too low, resulting in too low yield of Na(NH ₄ )TaF ₇ polycrystalline particles. If the ratio of the added molar amount of tantalum source to the amount of HF solution is greater than 4mmol/L, the hydrofluoric acid aqueous solution used to dissolve the tantalum source is too small, the tantalum source is not completely dissolved, but the first precursor solution has reached the saturated concentration of tantalum, which also makes the yield of Na(NH ₄ )TaF ₇ too low.

Preferably, the ratio of the added molar amount of the tantalum source to the volume of the hydrofluoric acid aqueous solution is 2 mmol/mL.

Preferably, the concentration of the hydrofluoric acid aqueous solution is 20 to 60 wt %.

Preferably, the concentration of the hydrofluoric acid aqueous solution is 40 wt %.

Preferably, in S2, the ratio of the sum of the added molar amounts of the sodium source and the ammonium source to the volume of deionized water is 1 to 2.5 mmol/mL.

By adjusting the feeding amount of sodium source, ammonium source and deionized water, the ratio of the sum of the added molar amounts of sodium source and ammonium source to the volume of deionized water is 1-2.5mmol/mL, which can improve the yield and purity of Na(NH ₄ )TaF _7. If the ratio of the sum of the added molar amounts of sodium source and ammonium source to the volume of deionized water is less than 1mmol/L, the concentrations of sodium ions and ammonium ions are too low, affecting the yield of Na(NH ₄ )TaF ₇ ; if the ratio of the sum of the added molar amounts of sodium source and ammonium source to the volume of deionized water is greater than 2.5mmol/L, the obtained Na(NH ₄ )TaF ₇ contains more impurities, thereby reducing the purity of Na(NH ₄ )TaF ₇ .

Preferably, the amount of deionized water added is 10-40 ml.

Preferably, the amount of deionized water added is 20 ml.

Preferably, in S3, the molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is 0.005 to 0.1:1.

By adjusting the feed amount of the raw materials, the molar ratio of Mn ⁴⁺ ions to Na(NH ₄ )TaF ₇ is set to 0.005-0.1:1, so that the doping amount of Mn ⁴⁺ ions in the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ is 0.5%-10%, so that the doped material can emit red fluorescence.

Preferably, in S3, the feeding molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is 0.01:1.

Preferably, the ratio of the added molar amount of Na(NH ₄ )TaF ₇ to the volume of anhydrous ethanol is 0.025 to 0.05 mmol/mL.

By controlling the feeding amount of Na(NH ₄ )TaF ₇ and anhydrous ethanol, the ratio of the added molar amount of Na(NH ₄ )TaF ₇ to the volume of anhydrous ethanol is made to be 0.025-0.05mmol/L, so that the trace dissolved Na(NH ₄ )TaF ₇ can be precipitated by recrystallization to obtain the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ .

Preferably, the ratio of the added molar amount of Na(NH ₄ )TaF ₇ to the volume of anhydrous ethanol is 0.025 mmol/mL.

Preferably, the feeding amount of anhydrous ethanol is 5 to 10 mL.

Preferably, the feeding amount of anhydrous ethanol is 10 mL.

Preferably, the sodium source is selected from at least one of sodium fluoride, sodium bifluoride, and sodium carbonate; and/or the ammonium source is selected from at least one of ammonium fluoride, ammonium bifluoride, and ammonium carbonate; and/or the tantalum source includes tantalum pentoxide.

Preferably, the sodium source comprises sodium bifluoride.

Preferably, the ammonium source comprises ammonium bifluoride.

Preferably, the manganese source comprises potassium hexafluoromanganate.

According to a second aspect of the present invention, there is provided an application of the above-mentioned red fluorescent material in optical temperature measurement.

The luminescence intensity of the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ will change significantly with the change of temperature. By utilizing this temperature-dependent characteristic, the red fluorescent material can be applied to optical temperature measurement. By utilizing the luminescence intensity of the red fluorescent material at the temperature to be measured, the specific value of the temperature to be measured can be obtained. In addition, the red fluorescent material has a wide measurable temperature range, a wide range of application, and a high application prospect.

According to a third aspect of the present invention, there is provided an application method of the red fluorescent material, using ultraviolet light or blue light with a wavelength of 300 to 550 nm to excite the red fluorescent material.

The red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ used in this solution can be excited by light with a wavelength of 300-500nm and emit narrow-band red light of 580-680nm. When used in optical temperature measurement, the red fluorescent material Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ needs to be excited by light of the aforementioned wavelength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an XRD spectrum of a red fluorescent material provided in Example 2;

FIG2 is an excitation and emission spectrum diagram of a red fluorescent material provided in Example 2;

FIG3 is a light-emitting spectrum of the red fluorescent material provided in Example 2 at different temperatures;

FIG4 is a schematic diagram showing the relationship between the integrated intensity of the luminescence spectrum of the red fluorescent material provided in Example 2 and the temperature;

FIG. 5 is a schematic diagram showing the relationship between temperature and sensitivity of the red fluorescent material provided in Example 2.

DETAILED DESCRIPTION

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Example 1

This embodiment provides a red fluorescent material, whose chemical composition is Na(NH ₄ )TaF ₇ :0.5% Mn ⁴⁺ . The tantalum source selected for the red fluorescent material is Ta ₂ O ₅ ; the concentration of the hydrofluoric acid aqueous solution selected is 40wt%, the sodium source selected is NaHF ₂ ; the ammonium source selected is NH ₅ F ₂ ; and the manganese source selected is K ₂ MnF ₆ .

The preparation method of the red fluorescent material comprises the following steps:

S1. 1.1047 g of tantalum source and 2.5 mL of hydrofluoric acid aqueous solution were mixed evenly, stirred for 20 min, and transferred to a high-pressure reactor, reacted at 150° C. for 16 hours, and cooled to room temperature to obtain a first precursor solution. The ratio of the added molar amount of tantalum source to the volume of hydrofluoric acid aqueous solution was 2 mmol/mL.

S2. 0.6199g of sodium source, 1.426g of ammonium source and 2.5mL of the first precursor solution were added to 20mL of deionized water in sequence, stirred for 20min to make the mixture uniform, transferred to a high-pressure reactor, reacted at 150°C for 16 hours, cooled to room temperature, washed the transparent polycrystals with deionized water and anhydrous ethanol for several times, and dried to obtain Na(NH ₄ )TaF ₇ . The ratio of the sum of the molar amounts of the sodium source and the ammonium source added to the volume of deionized water was 1.75nmol/mL.

S3. 0.0030g of manganese source was dissolved in a hydrofluoric acid aqueous solution to obtain a second precursor solution, and then 0.8874g of Na(NH ₄ )TaF ₇ was added to the second precursor solution to dissolve Na(NH ₄ )TaF ₇ , and then 10mL of anhydrous ethanol was added to the second precursor solution to recrystallize Na(NH ₄ )TaF ₇ :0.5% Mn ⁴⁺ , and the precipitate was centrifuged, and the precipitate obtained by centrifugation was washed with anhydrous ethanol for multiple times, filtered, and dried at 70°C for 8 hours to obtain a red fluorescent material. The molar ratio of manganese source to Na(NH ₄ )TaF ₇ was 0.005:1, and the ratio of the added molar amount of Na(NH ₄ )TaF ₇ to the volume of anhydrous ethanol was 0.025mmol/mL.

Example 2

This embodiment refers to the preparation method provided in Example 1 to prepare a red fluorescent material. The difference between this embodiment and Example 1 is that in the process of preparing the red fluorescent material, the molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is 0.01:1, and the chemical composition of the prepared red fluorescent material is Na(NH ₄ )TaF ₇ :1%Mn ⁴⁺ . Specifically, 0.0061gK ₂ MnF ₆ is used in S3 to replace the manganese source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 1.

Example 3

This embodiment refers to the preparation method provided in Example 1 to prepare a red fluorescent material. The difference between this embodiment and Example 1 is that in the process of preparing the red fluorescent material, the molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is 0.1:1, and the chemical composition of the prepared red fluorescent material is Na(NH ₄ )TaF ₇ :10%Mn ⁴⁺ . Specifically, 0.0617gK ₂ MnF ₆ is used in S3 to replace the manganese source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 1.

Example 4

This example prepares a red fluorescent material with reference to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the ratio of the added molar amount of the tantalum source to the volume of the hydrofluoric acid aqueous solution is 1 mmol/L, specifically, in S1, 0.5523 g Ta ₂ O ₅ is added to replace the tantalum source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Example 5

This example prepares a red fluorescent material with reference to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the ratio of the added molar amount of the tantalum source to the volume of the hydrofluoric acid aqueous solution is 4 mmol/L, specifically, in S1, 2.2094 g Ta ₂ O ₅ is added to replace the tantalum source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Example 6

This example prepares a red fluorescent material with reference to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the ratio of the sum of the added molar amounts of the sodium source and the ammonium source to the volume of deionized water is 1.25 mmol/L, specifically, in S2, 0.3099 g NaHF ₂ and 1.1408 g NH ₅ F ₂ are used to replace the sodium source and ammonium source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Example 7

This example prepares a red fluorescent material by referring to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the ratio of the sum of the added molar amounts of the sodium source and the ammonium source to the volume of deionized water is 2.5 mmol/L, specifically, in S2, 1.5497 g NaHF ₂ is added to replace the sodium source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Example 8

This example prepares a red fluorescent material by referring to the preparation method provided in Example 2. The difference between this example and Example 2 is that NaF is used as a sodium source in the process of preparing the red fluorescent material. The rest of the raw material ratios and preparation methods are strictly consistent with those in Example 2.

Embodiment 9

This example prepares a red fluorescent material by referring to the preparation method provided in Example 2. The difference between this example and Example 2 is that NH ₄ F is used as the sodium source in the process of preparing the red fluorescent material. The other raw material ratios and preparation methods are strictly consistent with those in Example 2.

Example 10

This example prepares a red fluorescent material with reference to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the reaction temperature and reaction time in S1 and S2 are changed, specifically, both S1 and S2 are reacted at 180°C for 10 hours. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Embodiment 11

This example prepares a red fluorescent material with reference to the preparation method provided in Example 2. The difference between this example and Example 2 is that in the process of preparing the red fluorescent material, the reaction temperature and reaction time in S1 and S2 are changed, specifically, both S1 and S2 are reacted at 100°C for 24 hours. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Comparative Example 1

This comparative example refers to the preparation method provided in Example 2 to prepare a red fluorescent material. The difference between this comparative example and Example 2 is that in the process of preparing the red fluorescent material, the molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is 0.001:1, and the chemical composition of the prepared red fluorescent material is Na(NH ₄ )TaF ₇ :0.1% Mn ⁴⁺ . Specifically, 0.002g K ₂ MnF ₆ is used in S3 to replace the manganese source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Comparative Example 2

This comparative example refers to the method for preparing a red fluorescent material provided in Example 2 to prepare a red fluorescent material. The difference between this comparative example and Example 2 is that in the process of preparing the red fluorescent material, the molar ratio of the manganese source to Na(NH ₄ )TaF ₇ is n(Mn ⁴⁺ ):n(Ta)=0.15:1, and the chemical composition of the prepared red fluorescent material is Na(NH ₄ )TaF ₇ :15% Mn ⁴⁺ . Specifically, 0.0927g K ₂ MnF ₆ is used in S3 to replace the manganese source used in Example 2. The rest of the raw material ratios and preparation methods are strictly consistent with Example 2.

Comparative Example 3

This comparative example refers to the method for preparing a red fluorescent material provided in Example 2 to prepare a material containing Na(NH ₄ )TaF _7. The difference between this comparative example and Example 2 is that the recrystallization operation in S3 is omitted, specifically, the operation step of adding anhydrous ethanol to the second precursor solution is omitted. The prepared material contains Na(NH ₄ )TaF ₇ , but Mn ⁴⁺ is not doped into Na(NH ₄ )TaF _7. The rest of the raw material ratios and preparation methods are strictly consistent with those in Example 2.

Test Case

Test objects: red fluorescent materials prepared in Examples 1 to 11, and materials prepared in Comparative Examples 1 to 3.

Test items and test methods:

(1) X-ray powder diffraction

The X-ray diffraction patterns (XRD) of the test objects were collected by Bruker D8 Advance X-ray diffractometer, using Cu-Kα target as the radiation source (λ=0.15406nm), working voltage of 40kV, working current of 40mA, and 2θ scanning range of 5-90°.

(2) Fluorescence spectroscopy

The samples were excited at temperatures ranging from 83 to 448 K, and the emission spectra were collected on an Edinburgh Instrument FS5 steady-state-transient fluorescence spectrometer equipped with a 450 W xenon lamp and an SC-05 variable temperature controller.

Test results: By comparing the test results of the red fluorescent materials provided in Examples 1 to 11 with the corresponding test results of the materials prepared in Comparative Examples 1 to 3, it can be found that the luminescence intensity of the red fluorescent materials prepared in Comparative Examples 1 to 2 is lower than that measured in Examples 1 to 11. Among them, the Mn ⁴⁺ doping amount in the red fluorescent material provided in Comparative Example 1 is too small, and the Mn ⁴⁺ doping amount in the red fluorescent material provided in Comparative Example 2 is too large. This shows that if the doping amount of Mn ⁴⁺ in the material is too small, the optimal concentration that the material can accommodate is not reached, and the luminescence intensity of the material is low; if the doping amount of Mn ⁴⁺ in the material is too much, concentration quenching is likely to occur, resulting in a low luminescence intensity of the material. Since the temperature measurement resolution depends on the luminescence intensity of the material, the optical application of the red fluorescent materials provided in Comparative Examples 1 to 2 will be limited. Since the material provided in Comparative Example 3 is not prepared by the recrystallization method, Mn ⁴⁺ cannot be smoothly doped into Na(NH ₄ )TaF ₇ , which is equivalent to a doping amount close to 0%, so the material provided in Comparative Example 3 cannot emit light either. The red fluorescent materials provided in Examples 1 to 11 can be excited by ultraviolet light or blue light with a wavelength of 300 to 550 nm, and emit narrow-band red light with a wavelength of 580 to 680 nm, and the light with a wavelength of 628.8 nm has the highest luminous intensity. This shows that the red fluorescent materials provided in Examples 1 to 11 with NaNH ₄ TaF ₇ as a matrix, Mn ⁴⁺ as an activator, a chemical composition of Na(NH ₄ )TaF ₇ :xMn ⁴⁺ , and 0.5%≤x≤10% can emit red light, and their luminous intensity responds sensitively to temperature changes, and has temperature-dependent characteristics in a wide temperature range. The red fluorescent material has the characteristics of fast response speed, high temperature measurement sensitivity, and a wide temperature measurement range, and has the potential to be applied in the field of optical temperature measurement.

Among them, Na(NH ₄ )TaF ₇ :1% Mn ⁴⁺ prepared in Example 2 has the best temperature measurement sensitivity and the widest temperature measurement range among the red fluorescent materials prepared in Examples 1 to 11. The test spectra of the red fluorescent material Na(NH ₄ )TaF ₇ :1% Mn ⁴⁺ provided in Example 2 are shown in FIGS.

Figure 1 is an XRD spectrum of the red fluorescent material Na( _NH4 ) _TaF7 :1%Mn4 ⁺ provided in Example 2. As can be seen from Figure 1, the XRD diffraction peaks of the prepared material are consistent with the standard card PDF#00-057-0546, indicating that the Na( _NH4 ) _TaF7 :1%Mn4 ⁺ prepared in Example 2 is a pure phase.

Figure 2 is an excitation and emission spectrum diagram of the red fluorescent material Na(NH ₄ )TaF ₇ :1% Mn ⁴⁺ provided in Example 2. As can be seen from Figure 2, the excitation spectrum of the red fluorescent material Na(NH ₄ )TaF ₇ :1% Mn ⁴⁺ consists of two broad peaks with central wavelengths of 358nm and 473nm, wherein the strongest excitation is at 473nm, and the emission is a narrow-band red light of 580-680nm, with the strongest wavelength at 628.8nm.

Figure 3 is the luminescence spectrum at different temperatures of the red fluorescent material provided in Example 2. As can be seen from Figure 3, with the increase of temperature, the total luminescence intensity of the red fluorescent material Na(NH ₄ )TaF ₇ :1% Mn ⁴⁺ shows a significant downward trend.

Figure 4 is a schematic diagram showing the relationship between the integrated intensity of the luminescence spectrum and temperature of the red fluorescent material provided in Example 2. From Figure 4, it can be more intuitively found that the red fluorescent material has high sensitivity to temperature changes, and the red fluorescent material has temperature variation characteristics within the temperature range of 240-440K.

Figure 5 is a schematic diagram showing the relationship between temperature and sensitivity of the red fluorescent material provided in Example 2. As shown in Figure 5, the red fluorescent material Na( _NH4 ) _TaF7 :1%Mn4 ⁺ provided in Example 2 achieves the highest absolute sensitivity of 0.0122K ^-1 at 323K and the highest relative sensitivity of 2.48%K ^-1 at 348K.

The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims (9)

1. A red fluorescent material, characterized in that it uses NaNH ₄ TaF ₇ as a matrix, Mn ⁴⁺ as an activator, and has a chemical composition of Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ , 0.5%≤x≤10%; the red fluorescent material is prepared by the following steps: S1. The tantalum source and the hydrofluoric acid aqueous solution are mixed uniformly and reacted at 100 to 180 ° C for 7 to 24 hours to obtain a first precursor solution; S2. Then, the sodium source, the ammonium source, the deionized water and the first precursor solution are mixed evenly, and reacted at 100 to 180° C. for 7 to 24 hours to obtain Na(NH ₄ )TaF ₇ ; S3. Evenly mix the manganese source and the hydrofluoric acid aqueous solution to obtain a second precursor solution, then add the Na(NH ₄ )TaF ₇ to the second precursor solution to dissolve the Na(NH ₄ )TaF ₇ , and add anhydrous ethanol to the second precursor solution to recrystallize and precipitate Na(NH ₄ )TaF ₇ :x Mn ⁴⁺ to obtain the red fluorescent material. 2. The red fluorescent material according to claim 1, characterized in that, in S1, the ratio of the added molar amount of the tantalum source to the volume of the hydrofluoric acid aqueous solution is 1 to 4 mmol/mL. 3 . The red fluorescent material according to claim 2 , wherein the concentration of the hydrofluoric acid aqueous solution is 20 to 60 wt %. 4. The red fluorescent material according to claim 1, characterized in that, in S2, the ratio of the sum of the added molar amounts of the sodium source and the ammonium source to the volume of the deionized water is 1 to 2.5 mmol/mL. 5 . The red fluorescent material according to claim 1 , characterized in that, in S3 , the molar ratio of the manganese source to the Na(NH ₄ )TaF ₇ is 0.005 to 0.1:1. 6 . The red fluorescent material according to claim 1 , wherein the ratio of the added molar amount of the Na(NH ₄ )TaF ₇ to the volume of the anhydrous ethanol is 0.25 to 0.05 mmol/mL. 7. The red fluorescent material according to claim 1, wherein the sodium source is selected from at least one of sodium fluoride, sodium bifluoride and sodium carbonate; And/or, the ammonium source is selected from at least one of ammonium fluoride, ammonium bifluoride and ammonium carbonate; And/or, the tantalum source includes tantalum pentoxide. 8. Use of the red fluorescent material according to any one of claims 1 to 7 in optical temperature measurement. 9 . The method for applying the red fluorescent material according to claim 1 , wherein the red fluorescent material is excited by ultraviolet light or blue light with a wavelength of 300 to 550 nm.