Single chromium-doped near-infrared hexagonal aluminate luminescent material and preparation method thereof

Abstract

The invention is applicable to the technical field of luminescent materials, and provides a single chromium-doped near-infrared hexagonal aluminate luminescent material, the chemical general formula of the luminescent material is La < 0.827 > Al < 11.9 > (1-x) Cr < 11.9 > x O < 19.09 >, and x is greater than or equal to 0.2% and less than or equal to 2.2%. The invention also provides a preparation method of the single chromium-doped near-infrared hexagonal aluminate luminescent material. The invention also provides an application of the single chromium-doped near-infrared hexagonal aluminate luminescent material in preparation of a near-infrared LED device excited by a blue light chip. According to the invention, Cr < 3 + > ions are used as an activator, a main excitation peak is located at 468 nm, near-infrared efficient luminescence can be realized under blue light excitation, an emission peak value is 934 nm, and an emission range can cover 600-1400 nm; in addition, La0. 827Al1. 9O19.09: Cr < 3 + > shows high thermal stability and high quantum efficiency, the luminous intensity at 140 DEG C is 77.32% of the luminous intensity at room temperature (20 DEG C), and the quantum efficiency is as high as 74.88%.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent materials, and in particular relates to a single chromium-doped near-infrared hexagonal aluminate luminescent material and a preparation method thereof. Background Art

[0002] Near-infrared (NIR, 700-2500 nm) spectroscopy technology 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 ingredient 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 substances can be simultaneously identified by near-infrared light sources. Therefore, high-quality near-infrared light sources are urgently needed to identify as many components as possible. In addition, low-energy photons of near-infrared light have excellent penetration depth and signal-to-noise ratio in human tissues due to low spontaneous fluorescence and light scattering. The luminescent material with NIR luminescence characteristics is coated on a commercial blue light LED chip, and the blue light emitted by the chip is used to excite the NIR phosphor to obtain a NIR pc-LED light source, which is likely to replace traditional halogen lamps, incandescent lamps, gallium arsenide LEDs (narrow-band near-infrared emission) and medical micro-devices, thereby solving related problems such as high temperature, large size, and high energy consumption. With the development of scale, diversification, and multi-mode data processing of smart devices, integrating near-infrared spectrometers as a functional module into portable smart terminal devices is expected to solve problems such as non-destructive testing and instant analysis of daily food, drugs, clothing, etc. However, the quantum efficiency of near-infrared phosphors reported in recent years is generally low and cannot achieve 100% internal quantum efficiency. At the same time, thermal stability also needs to be improved urgently. Therefore, the development of near-infrared luminescent materials that are efficient, thermally stable, and can be effectively excited by blue light is still a daunting challenge.

[0003] In recent years, hexagonal lanthanum aluminate has become a widely used transition metal and rare earth ion carrier material, which has attracted attention due to its excellent low thermal conductivity, high corrosion resistance and high thermal stability. From a crystallographic point of view, its crystal structure is a magnetoplumbite structure with a P63 / mmc space group. Hexagonal aluminates doped with impurities have been successfully synthesized and characterized. However, La 0.827 Al 11.9 O 19.09 It has not received much attention as a luminous host. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a single chromium-doped near-infrared hexagonal aluminate luminescent material, aiming to solve the problems raised in the above background technology.

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

[0006] Another object of the embodiment of the present invention is to provide a method for preparing a single chromium-doped near-infrared hexagonal aluminate luminescent material, comprising the following steps: According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 , weighing raw materials 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 are compounds containing La, Al, and Cr elements respectively; The weighed raw materials are added to a dispersant and ground thoroughly until the dispersant evaporates to obtain a uniform white powder. The ground white powder is sintered at 1450° C. for 4 hours, and then slowly cooled to room temperature until cooled to obtain the single chromium-doped near-infrared hexagonal aluminate luminescent material.

[0007] Preferably, in step (1), the compound containing the La element is one of La(OH)3, La2O3, La(NO3)3, and La2(SO4)3.

[0008] Preferably, in step (1), the compound containing the Al element is one of Al2O3, Al(OH)3, AlCl3, Al2(SO4)3, and Al(NO3)3.

[0009] Preferably, in step (1), the compound containing the Cr element is one of Cr2O3, Cr(OH)3, and Cr2(SO4)3.

[0010] Preferably, in step (2), the dispersant is anhydrous ethanol.

[0011] Another object of an embodiment of the present invention is to provide an application of a single chromium-doped near-infrared hexagonal aluminate luminescent material in preparing a near-infrared LED device excited by a blue light chip.

[0012] A near-infrared hexagonal aluminate luminescent material La doped with chromium provided in an embodiment of the present invention 0.827 Al 11.9 O 19.09 :Cr 3+ , with Cr 3+ions are activators, with the main excitation peak at 468 nm. Under blue light excitation, they can achieve efficient near-infrared luminescence, with an emission peak at 934 nm and an emission range of 600-1400 nm. 0.827 Al 11.9 O 19.09 : Cr 3+ It exhibits high thermal stability and high quantum efficiency. At 140°C, the luminous intensity is 77.32% of the luminous intensity at room temperature (20°C), and the quantum efficiency is as high as 74.88%; The raw material resources used in the embodiments of the present invention are abundant in reserves, the preparation method is simple and easy, 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 and development of near-infrared materials and the optimization of application performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 XRD patterns of the materials prepared in Examples 1-6 and Comparative Example 1 of the present invention; Figure 2 This is the excitation emission spectrum of the material prepared in Example 3 of the present invention; Figure 3 This is an excitation spectrum of the materials prepared in Examples 1-6 of the present invention under 934nm monitoring; Figure 4 This is an emission spectrum of the material prepared in Examples 1-6 of the present invention under 468nm excitation; Figure 5 This is a thermal quenching curve diagram of the material prepared in Example 3 of the present invention; Figure 6 This is a diagram of the quantum efficiency of the material prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09, accurately weigh the corresponding raw materials using an electronic balance according to the molar ratio of each element La:Al:Cr=0.827:11.9(1-x):11.9x, x is 0.2%≤x≤2.2%, wherein the raw materials are La source, Al source, and Cr source respectively; The La source is an oxide containing La or a compound that can be converted into the oxide; The Al source is an oxide containing Al or a compound that can be converted into the oxide; The Cr source contains Cr oxide, chloride or carbonate; (2) The weighed raw materials are placed in an agate mortar, and anhydrous ethanol is added as a dispersant to grind the raw materials thoroughly until the alcohol evaporates and a uniform powder is obtained. The ground powder is placed in an alumina crucible, and the crucible is placed in a muffle furnace at 1450° C. and fired for 4 h. The temperature is then slowly lowered to room temperature until it cools down, thereby obtaining the single chromium-doped near-infrared hexagonal aluminate fluorescent material.

[0016] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0017] Embodiment 1: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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, Cr2O3, accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0018] Embodiment 2: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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 accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0019] Embodiment 3: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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 accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0020] Embodiment 4: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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 accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0021] Example 5: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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 accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0022] Embodiment 6: A single chromium-doped near-infrared hexagonal aluminate luminescent material, the preparation method of which comprises the following steps: (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 accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 minutes to make the raw materials evenly mixed to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and burn it at 1450°C for 4 hours, then slowly cool it to room temperature until it cools down.

[0023] Comparative Example 1: A hexagonal aluminate material, the preparation method of which comprises the following steps: (1) According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0), that is, La 0.827 Al 11.9 O 19.09 Composition: accurately weigh La2O3, Al2O3, Cr2O3, add appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain mixed powder; (2) Place the mixed powder into an alumina crucible, place the crucible in a muffle furnace and sinter at 1450°C for 4 hours, then slowly cool to room temperature until cooled.

[0024] Performance Test: The samples prepared in Comparative Example 1 and Examples 1-6 were analyzed using powder X-ray diffraction (XRD) technology to obtain XRD patterns as shown in Figure 1 As shown, it can be seen that the diffraction peak position of the luminescent material prepared in the embodiment of the present invention matches well with the standard card PDF#97-003-8371, and is a good single-phase sample; Figure 2 , Figure 3 and Figure 4 The excitation and emission spectra of the samples prepared in Examples 1-6 are given; it can be seen that the excitation spectrum of the samples under 934nm monitoring shows an excitation peak in the range of 200-675nm, and there is strong excitation near 468nm; under 468nm excitation, the samples show near-infrared emission, the range extends from 600nm to around 1400nm, and the main emission peak wavelength is located near 934nm, indicating that it can be applied to near-infrared LEDs excited by blue light LED chips; and through spectral testing, the La prepared in Comparative Example 1 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 (x=0), that is, La 0.827 Al 11.9 O 19.09, there is no emission signal response under 468nm excitation, indicating that the sample has no near-infrared luminescence; Figure 5 The thermal quenching spectrum of the sample prepared in Example 3 is given. The results show that when the temperature rises to 413K (140°C), the emission intensity of the sample still maintains 77.32% of the initial intensity; Figure 6 The quantum efficiency diagram of the sample prepared in Example 3 is given, and 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.

[0025] In summary, the main excitation peak of the luminescent material prepared in the embodiment of the present invention is located at 468nm, which can effectively match the commercial blue light LED chip. Under blue light excitation, its emission spectrum covers 600-1400nm, and the main emission peak is located at 934nm. The emission of the material shows excellent thermal quenching and is accompanied by excellent photoluminescence efficiency.

[0026] 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 in the protection scope of the present invention.

Claims

1. A near-infrared hexagonal aluminate luminescent material doped with chromium, characterized in that: 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%.

2. A method for preparing the single chromium-doped near-infrared hexagonal aluminate luminescent material according to claim 1, characterized in that: The following steps are involved: According to the chemical formula La 0.827 Al 11.9(1-x) Cr 11.9x O 19.09 , weighing raw materials 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 are compounds containing La, Al, and Cr elements respectively; The weighed raw materials are added to a dispersant and ground thoroughly until the dispersant evaporates to obtain a uniform white powder. The ground white powder is sintered at 1450° C. for 4 hours, and then slowly cooled to room temperature until cooled to obtain the single chromium-doped near-infrared hexagonal aluminate luminescent material.

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

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

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

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

7. Use of the single chromium-doped near-infrared hexagonal aluminate luminescent material as claimed in claim 1 in preparing a near-infrared LED device excited by a blue light chip.

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