A single-doped chromium near-infrared hexaaluminate luminescent material and a preparation method thereof

Abstract

This invention relates to the field of luminescent materials technology and provides a chromium-doped near-infrared hexagonal aluminate luminescent material, wherein the chemical formula of the luminescent material is La. 0.827 Al 11.9(1‑x) Cr 11.9x O 19.09 Furthermore, 0.2% ≤ x ≤ 2.2%. This invention also provides a method for preparing a chromium-doped near-infrared hexagonal aluminate luminescent material. This invention further provides the application of the chromium-doped near-infrared hexagonal aluminate luminescent material in the preparation of near-infrared LED devices excited by blue light chips. This invention uses Cr... 3+ Using ions as activators, the main excitation peak is located at 468 nm. Under blue light excitation, it can achieve highly efficient near-infrared luminescence with an emission peak of 934 nm and an emission range covering 600-1400 nm. Furthermore, La... 0.827 Al 11.9 O 19.09 :Cr 3+ It exhibits high thermal stability and high quantum efficiency, with a luminescence intensity at 140℃ that is 77.32% of the luminescence intensity at room temperature (20℃), and a quantum efficiency as high as 74.88%.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, and particularly relates to a chromium-doped near-infrared hexagonal aluminate luminescent material and its preparation method. Background Technology

[0002] Near-infrared (NIR, 700-2500 nm) spectroscopy has had a profound impact on innovations in traditional fields such as night vision, remote control, and security systems, as well as emerging fields such as biological imaging, plant growth, food component identification, iris recognition, and targeted therapy. Quantitative analysis of multiple compounds is a hot topic in food science research. Low-frequency NIR light has a wide absorption effect on OH, CH, and NH bonds. Complex molecular overtones and stretching vibrations in different organic compounds can be simultaneously identified by near-infrared light sources. Therefore, there is an urgent need for high-quality near-infrared light sources to identify as many components as possible. In addition, the low-energy photons of near-infrared light have excellent penetration depth and signal-to-noise ratio in human tissues due to their low autofluorescence and light scattering. Coating luminescent materials with NIR luminescence properties onto commercial blue LED chips and using the blue light emitted by the chip to excite NIR phosphors can produce NIR pc-LED light sources, which may replace traditional halogen lamps, incandescent lamps, gallium arsenide LEDs (narrowband near-infrared emitters), and medical microdevices, thereby solving problems related to high temperature, large size, and high energy consumption. With the development of large-scale, diversified, and multimodal data processing of intelligent devices, integrating near-infrared spectrometers as a functional module into portable intelligent terminal devices is expected to solve the problems of non-destructive testing and real-time analysis of everyday food, medicines, clothing, etc. However, the quantum efficiency of near-infrared phosphors reported in recent years is generally low, and it is impossible to achieve 100% internal quantum efficiency. At the same time, thermal stability also urgently needs to be improved. Therefore, developing efficient, thermally stable, and blue light-excited near-infrared luminescent materials remains a formidable challenge.

[0003] In recent years, lanthanum hexagonal aluminate has become a widely used transition metal and rare earth ion carrier material, attracting attention due to its excellent low thermal conductivity, high corrosion resistance, and high thermal stability. From a crystallographic perspective, its crystal structure is a magnetoplumboid type with space group P63 / mmc. Doped hexagonal aluminates have been successfully synthesized and characterized; however, La... 0.827 Al 11.9 O 19.09 As a bioluminescent host, it has not received much attention. Summary of the Invention

[0004] The purpose of this invention is to provide a chromium-doped near-infrared hexagonal aluminate luminescent material, which aims to solve the problems mentioned in the background art.

[0005] The present invention is implemented as follows: a chromium-doped near-infrared hexagonal aluminate luminescent material, wherein the chemical formula of the luminescent material is La. 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 And 0.2%≤x≤2.2%.

[0006] Another objective of this invention is to provide a method for preparing a chromium-doped near-infrared hexagonal aluminate luminescent material, comprising the following steps:

[0007] According to the general chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 Raw materials were weighed according to the molar ratio of each element La:Al:Cr = 0.827:11.9(1-x):11.9x, wherein 0.2%≤x≤2.2%, and the raw materials were compounds containing La, Al, and Cr elements respectively.

[0008] The weighed raw materials are added to the dispersant and ground thoroughly until the dispersant evaporates to obtain a uniform white powder. The ground white powder is then calcined at 1450°C for 4 hours and then slowly cooled to room temperature until cooled to obtain the chromium-doped near-infrared hexagonal aluminate luminescent material.

[0009] Preferably, in step (1), the La-containing compound is one of La(OH)3, La2O3, La(NO3)3, and La2(SO4)3.

[0010] Preferably, in step (1), the Al-containing compound is one of Al2O3, Al(OH)3, AlCl3, Al2(SO4)3, and Al(NO3)3.

[0011] Preferably, in step (1), the Cr-containing compound is one of Cr2O3, Cr(OH)3, and Cr2(SO4)3.

[0012] Preferably, in step (2), the dispersant is anhydrous ethanol.

[0013] Another objective of this invention is to provide an application of a chromium-doped near-infrared hexagonal aluminate luminescent material in the fabrication of near-infrared LED devices excited by blue light chips.

[0014] This invention provides a chromium-doped near-infrared hexagonal aluminate luminescent material, La. 0.827 Al 11.9 O 19.09 :Cr 3+ , with Cr 3+Using ions as activators, the main excitation peak is located at 468 nm. Under blue light excitation, it can achieve highly efficient near-infrared luminescence with an emission peak of 934 nm and an emission range covering 600-1400 nm. Furthermore, La... 0.827 Al 11.9 O 19.09 : Cr 3+ It exhibits high thermal stability and high quantum efficiency, with a luminescence intensity at 140℃ that is 77.32% of the luminescence intensity at room temperature (20℃), and a quantum efficiency as high as 74.88%.

[0015] The raw materials used in the embodiments of this invention are abundant, the preparation method is simple and easy to implement, the physicochemical stability is good, the fluorescence lifetime is ideal, and it is green and pollution-free. It can effectively meet the needs of near-infrared LED devices and provide new ideas for the design, development and application performance optimization of near-infrared materials. Attached Figure Description

[0016] Figure 1 The XRD patterns of the materials prepared in Examples 1-6 and Comparative Example 1 of this invention are shown below.

[0017] Figure 2 The excitation-emission spectrum of the material prepared in Example 3 of this invention;

[0018] Figure 3 The following are excitation spectra of the materials prepared in Examples 1-6 of this invention under 934 nm monitoring.

[0019] Figure 4 The emission spectra of the materials prepared in Examples 1-6 of this invention under 468 nm excitation are shown.

[0020] Figure 5 This is a thermal quenching curve of the material prepared in Example 3 of the present invention;

[0021] Figure 6 This is a quantum efficiency diagram of the material prepared in Example 3 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0024] (1) According to the general chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O19.09 According to the molar ratio of each element La:Al:Cr = 0.827:11.9(1-x):11.9x, the corresponding raw materials were accurately weighed using an electronic balance, with x being 0.2%≤x≤2.2%, and the raw materials being La source, Al source, and Cr source, respectively.

[0025] The La source is an oxide containing La or a compound that can be converted into that oxide;

[0026] The Al source is an oxide containing Al or a compound that can be converted into such an oxide;

[0027] The Cr source is a Cr oxide, chloride, or carbonate.

[0028] (2) Place the weighed raw materials into an agate mortar, add anhydrous ethanol as a dispersant and grind thoroughly until the alcohol evaporates to obtain a uniform powder. Place the ground powder into an alumina crucible, place the crucible in a muffle furnace at 1450°C and fire for 4 hours, then slowly lower it to room temperature until cooled to obtain the single chromium-doped near-infrared hexagonal aluminate fluorescent material.

[0029] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0030] Example 1: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0031] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0.002) The initial raw materials are La2O3, Al2O3 and Cr2O3. They are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant. The mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0032] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly cool it to room temperature until it is cooled.

[0033] Example 2: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0034] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09(x=0.006) The initial raw materials are La2O3, Al2O3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio. An appropriate amount of anhydrous ethanol is added as a dispersant and the mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0035] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly reduce it to room temperature until cooled.

[0036] Example 3: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0037] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0.010) The initial raw materials are La2O3, Al2O3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio. An appropriate amount of anhydrous ethanol is added as a dispersant and the mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0038] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly reduce it to room temperature until cooled.

[0039] Example 4: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0040] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0.014) The initial raw materials are La2O3, Al2O3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio. An appropriate amount of anhydrous ethanol is added as a dispersant and the mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0041] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly reduce it to room temperature until cooled.

[0042] Example 5: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0043] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09(x=0.018) The initial raw materials are La2O3, Al2O3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio. An appropriate amount of anhydrous ethanol is added as a dispersant and the mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0044] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly cool it to room temperature until it is cooled.

[0045] Example 6: A chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which includes the following steps:

[0046] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0.022) The initial raw materials are La2O3, Al2O3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio. An appropriate amount of anhydrous ethanol is added as a dispersant and the mixture is ground for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder.

[0047] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450℃ for 4 hours, and then slowly cool it to room temperature until it is cooled.

[0048] Comparative Example 1: A hexagonal aluminate material, the preparation method of which includes the following steps:

[0049] (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0), i.e., La 0.827 Al 11.9 O 19.09 The composition is as follows: accurately weigh La2O3, Al2O3, and Cr2O3, add an appropriate amount of anhydrous ethanol as a dispersant, and grind thoroughly for 30 minutes to obtain a mixed powder.

[0050] (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace at 1450°C for 4 hours and then slowly reduce it to room temperature until it cools down.

[0051] Performance testing:

[0052] The samples prepared in Comparative Example 1 and Examples 1-6 were analyzed using powder X-ray diffraction (XRD) technology, and the XRD patterns were obtained as follows: Figure 1As shown, the diffraction peak positions of the luminescent material prepared in the embodiments of the present invention match well with the standard card PDF#97-003-8371, indicating that it is a good single-phase sample.

[0053] Figure 2 , Figure 3 and Figure 4 The excitation and emission spectra of the samples prepared in Examples 1-6 are presented. It can be seen that the excitation spectrum of the samples under 934 nm monitoring exhibits an excitation peak in the range of 200-675 nm, with strong excitation near 468 nm. Under 468 nm excitation, the samples exhibit near-infrared emission, extending from 600 nm to around 1400 nm, with the main emission peak wavelength located near 934 nm, indicating its applicability to near-infrared LEDs excited by blue LED chips. Meanwhile, through spectral testing, the La... (The sentence is incomplete and requires further context to translate accurately.) 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0), i.e., La 0.827 Al 11.9 O 19.09 The absence of emission signal response under 468nm excitation indicates that the sample does not emit near-infrared light.

[0054] Figure 5 The thermal quenching spectrum of the sample prepared in Example 3 is presented. The results show that when the temperature is increased to 413 K (140 °C), the emission intensity of the sample still retains 77.32% of the initial intensity.

[0055] Figure 6 The quantum efficiency diagram of the sample prepared in Example 3 is given. It can be seen that the quantum efficiency of the sample under 468nm excitation is 73.27%. The results show that the sample has high quantum efficiency and has the potential to be applied to high-efficiency near-infrared LEDs.

[0056] In summary, the luminescent material prepared in the embodiments of the present invention has a main excitation peak at 468 nm, which can effectively match commercial blue LED chips. Under blue light excitation, its emission spectrum covers 600-1400 nm, with the main emission peak at 934 nm. The material exhibits excellent thermal quenching and is accompanied by excellent photoluminescence efficiency.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A chromium-doped near-infrared hexagonal aluminate luminescent material, characterized in that, The general chemical formula of the luminescent material is La. 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 And 0.2%≤x≤2.2%.

2. A method for preparing a chromium-doped near-infrared hexagonal aluminate luminescent material as described in claim 1, characterized in that, Includes the following steps: According to the general chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 Raw materials were weighed according to the molar ratio of each element La:Al:Cr = 0.827:11.9(1-x):11.9x, wherein 0.2%≤x≤2.2%, and the raw materials were compounds containing La, Al, and Cr elements respectively. The weighed raw materials are added to the dispersant and ground thoroughly until the dispersant evaporates to obtain a uniform white powder. The ground white powder is then calcined at 1450°C for 4 hours and then slowly cooled to room temperature until cooled to obtain the chromium-doped near-infrared hexagonal aluminate luminescent material.

3. The method for preparing a single-chromium-doped near-infrared hexagonal aluminate luminescent material according to claim 2, characterized in that, In step (1), the La-containing compound is one of La(OH)3, La2O3, La(NO3)3, and La2(SO4)3.

4. The method for preparing a single-chromium-doped near-infrared hexagonal aluminate luminescent material according to claim 2, characterized in that, In step (1), the Al-containing compound is one of Al2O3, Al(OH)3, AlCl3, Al2(SO4)3, and Al(NO3)3.

5. The method for preparing a chromium-doped near-infrared hexagonal aluminate luminescent material according to claim 2, characterized in that, In step (1), the Cr-containing compound is one of Cr2O3, Cr(OH)3, or Cr2(SO4)3.

6. The method for preparing a chromium-doped near-infrared hexagonal aluminate luminescent material according to claim 2, characterized in that, In step (2), the dispersant is anhydrous ethanol.

7. The application of a single-chromium-doped near-infrared hexagonal aluminate luminescent material as described in claim 1 in the preparation of near-infrared LED devices excited by blue light chips.

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