A luminescent material having a significant spatial distribution of Mn 4+ Activated fluorescent ceramic materials and methods for making same

Abstract

The application discloses a Mn 4+ activated fluorescent ceramic material with significant spatial distribution of luminous efficiency and a preparation method thereof, and has a general formula of xMn 4+ Li3LaMg2TiO7 (x=0.05%~1%). The fluorescent material is prepared from MnO2, Li2CO3, La2O3, MgO and TiO2 as raw materials, through dry grinding and using distilled water as a binder to form a blank; the blank is then subjected to high-temperature solid-phase sintering to obtain the fluorescent ceramic material. Under the excitation of a 375 nm LED, red light emission of 711 nm can be obtained, and the quantum efficiency of the red light has significant spatial distribution characteristics. The quantum efficiency inside the ceramic reaches 23.6%, while the quantum efficiency of the outer surface significantly rises to 93.1%, about 4 times of the inner quantum efficiency; meanwhile, the luminous efficiency is also related to the shape, and the upper surface efficiency of a cylindrical body is the highest, followed by a spherical body and a cuboid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorescent ceramic preparation, and particularly relates to a Mn 4+ activated fluorescent ceramic material with a significant spatial distribution of luminescence efficiency and a preparation method thereof. BACKGROUND

[0002] Recently, Mn 4+ activated fluorescent materials have attracted increasing attention due to their abundant sources, economy, and wide absorption band. 2 E g → 4 A 2g forbidden transition emits red light and has good prospects in applications such as lighting, plant cultivation, temperature and pressure sensing. Literature reports show that not only in fluorides, but also in oxides, higher luminescence efficiency can be achieved, such as Malgorzata Rokicka pointed out that in Mn 4+ doped Gd2ZnTiO6 with a perovskite structure, the red light efficiency even reached 95.6%, which is very important for Mn 4+ activated red light materials; this is because compared with fluorides with poor thermal stability and environmental pollution, Mn 4+ activated red light materials based on oxides are more suitable for use in products such as lighting, plant cultivation and temperature sensing. Fluorescent materials are mainly divided into two categories: powder materials and bulk ceramics. Powder materials are so-called fluorescent powders, which have the advantages of easy integration with other substances and can be sprayed onto substrates according to the shape. Most of the Mn 4+ activated fluorescent materials reported so far belong to this category. On the other hand, compared with the use of traditional resin-encapsulated phosphors in LED lamps, bulk ceramics, i.e. fluorescent ceramics, exhibit more excellent mechanical properties and physicochemical stability, which makes them have more extensive use, such as laser technology, aerospace and other application fields.

[0003] However, traditional fluorescent ceramics mainly focus on the preparation, purity and mechanical stability of the ceramics, and the spatial distribution of the luminescent performance is relatively less studied. In fact, many fluorescent ceramics exhibit anisotropic luminescent performance, although this phenomenon is usually not obvious and is ignored by researchers. Based on this, the present application provides a Mn 4+ activated fluorescent ceramic material with a significant spatial distribution of luminescence efficiency and a preparation method thereof, and at the same time, in the study of the fluorescent properties of Mn 4+ : Li3LaMg2TiO7 ceramic material, it is observed that there is a strong correlation between the spatial distribution and the luminescence efficiency. In order to further explore the relationship between the spatial distribution change and the luminescence efficiency, we prepared ceramic samples with different geometric shapes and carried out a comprehensive analysis including crystal structure and luminescent properties. This is the first report of Mn4+ Li3LaMg2TiO7 ceramic material and exploration of fluorescent properties and brightness efficiency affected by spatial distribution change in Mn 4+ Li3LaMg2TiO7 ceramic material and exploration of fluorescent properties and brightness efficiency affected by spatial distribution change in Mn SUMMARY

[0004] The present application aims to provide a Mn 4+ activated fluorescent ceramic material and a preparation method thereof.

[0005] To achieve the above object, the present application adopts the following technical solution:

[0006] A Mn 4+ activated fluorescent ceramic material with significant spatial distribution of luminous efficiency, whose general formula is xMn 4+ :Li3LaMg2TiO7 (x=0.05 % ~ 1 %).

[0007] The xMn 4+ :Li3LaMg2TiO7 (x=0.05 % ~ 1 %) is prepared by selecting raw materials with high purity and uniform size, namely MnO2, Li2CO3, La2O3, MgO and TiO2, and proportioning according to the following equation:

[0008] x MnO2+0.5 La2O3+2MgO+(1-x) TiO2+1.5 Li2CO3→ x Mn:Li3LaMg2Ti （1-x） O7+1.5CO2↑

[0009] In the proportioning, x=0.05 % ~ 1 %.

[0010] The purity of the raw materials is respectively Li2CO3 (99.99 %), La2O3 (99.99 %), MgO (99.99 %), TiO2 (99.99 %) and MnO2 (99.95 %).

[0011] A preparation method of a Mn 4+ activated fluorescent ceramic material with significant spatial distribution of luminous efficiency, comprising the following steps:

[0012] (1) Each raw material is weighed according to the molar ratio of MnO2: La2O3: MgO: TiO2: Li2CO3 = x: 0.5: 2: (1-x): 1.5, wherein x=0.05 % ~ 1 %.

[0013] (2) Put each raw material into a marver and dry grind for 2 hours and mix evenly, use distilled water as a binder to make the material into a cylindrical, cuboid or spherical shape, and obtain a green body;

[0014] (3) Put the green body into a corundum crucible, and then place the corundum crucible in a tube furnace, and raise the temperature from room temperature to 900 DEG C, and keep the temperature constant for 3-5 h, and then continue to raise the temperature to 1100-1400 DEG C, and keep the temperature constant for 1-8 h in an air atmosphere, and then slowly reduce the temperature to 600 DEG C at a rate of 5 DEG C / min, and naturally cool to room temperature below 600 DEG C, and obtain the final xMn 4+ :Li3LaMg2TiO7 ceramic sample.

[0015] Further, the sintering temperature is 1300 DEG C and x=0.2 % are the optimal preparation conditions.

[0016] Further, the obtained ceramic sample is irradiated by an LED light source, and 711 nm red light emission is obtained.

[0017] Further, the wavelength of the LED light source is usually 375 nm.

[0018] Further, the 711 nm red light has a significant spatial distribution characteristic.

[0019] Further, the spatial distribution characteristic refers to that the external light emission efficiency of the ceramic is higher than the internal light emission efficiency, the upper surface light emission efficiency of the cylindrical ceramic is higher than the surface light emission efficiency of the spherical ceramic, and the surface light emission efficiency of the spherical ceramic material is higher than the surface light emission efficiency of the cuboid ceramic.

[0020] The advantages of the present application are:

[0021] 1. Compared with fluorescent powder, fluorescent ceramic has better thermal stability and mechanical properties, and the Mn 4+ :Li3LaMg2TiO7 fluorescent ceramic provided by the present application has a wider application field than the traditional Mn 4+ activated fluorescent powder.

[0022] 2. The Mn 4+ :Li3LaMg2TiO7 provided by the present application has very high light emission efficiency, and the quantum efficiency is as high as 93.1 %.

[0023] 3. The light emission efficiency of the Mn 4+ :Li3LaMg2TiO7 provided by the present application has a significant spatial distribution characteristic, and the internal quantum efficiency is only 23.6 %, while the external quantum efficiency is as high as 93.1 %, which is nearly 4 times different, making it particularly special.

[0024] 4. The present application is helpful for the exploration and research work in the field of high-efficiency fluorescent ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 2 (a) shows the xMn 4+ : XRD patterns of Li3LaMg2TiO7(x = 1%) samples. (b) is the Rietveld refinement of the sample (sintering temperature 1300 °C). (c) is the schematic diagram of the crystal structure of the sample.

[0026] Figure 2 Figure 3 (a) xMn 4+ : The fluorescence intensity of the internal region of Li3LaMg2TiO7(x = 0.05%~1%) samples prepared at 1300 °C varies with the doping concentration. (b) is the three-dimensional waterfall plot of the fluorescence intensity. (c) is the relationship between the fluorescence intensity of the internal region of the 0.2% Mn 4+ : The relationship between the fluorescence intensity of the internal region of the sample and the sintering temperature. (d) is the three-dimensional waterfall plot of the relationship.

[0027] Figure 3 Figure 4 (a) is xMn 4+ : The effect of the shape of Li3LaMg2TiO7(x = 0.2%) ceramic samples on the fluorescence intensity. (a) The effect of the shape of the ceramic on the fluorescence intensity of the external region. (b) The three-dimensional waterfall plot of the fluorescence intensity of the external region of the ceramic of different shapes. (c) The relationship between the fluorescence intensity of the upper surface of the cylinder and the sintering temperature. (d) The sample photo.

[0028] Figure 4 Figure 5 (a) is xMn 4+ : The luminescent efficiency of Li3LaMg2TiO7(x = 0.2%) ceramic. (a) The luminescent efficiency of the internal and external regions of the cylinder. (b) The luminescent efficiency of the spherical and cuboid surfaces. (c) The luminescent efficiency in the three-dimensional waterfall plot of the cylinder, sphere and cuboid. (d) The relationship between the luminescent efficiency and the spatial distribution. DETAILED DESCRIPTION

[0029] In order to make the content described in the present application more convenient to understand, the technical solutions described in the present application will be further described below in combination with specific embodiments, but the present application is not limited thereto.

[0030] Example 1

[0031] A Mn 4+ activated fluorescent ceramic material and a preparation method thereof, the technical scheme of which is as follows:

[0032] 1) Select MnO2, Li2CO3, La2O3, MgO and TiO2 with high purity and uniform size, and mix the raw materials according to the following equation:

[0033] x MnO2+0.5La2O3+2MgO+(1-x)TiO2+1.5Li2CO3→ xMn:Li3LaMg2Ti （1-x） O7+1.5CO2↑, wherein x is limited to one of 0.05%, 0.1%, 0.2%, 0.5%, 1%, respectively. Each raw material is weighed according to the molar ratio of MnO2: La2O3: MgO: TiO2: Li2CO3= x: 0.5: 2: (1-x): 1.5;

[0034] 2) Each raw material is placed in an agate mortar and dry ground for 2 h and mixed uniformly, and the material is made into a cylinder, a cuboid or a sphere using distilled water as a binder, to obtain a green body;

[0035] 3) The size of the cylindrical green body is 5 mm*10 mm*10 mm; the size of the cuboid is 20 mm*5 mm*5 mm; and the radius of the sphere is R=5 mm.

[0036] 4) The green body is placed in a corundum crucible, and the corundum crucible is placed in a tube furnace, which is raised from room temperature to 900°C, and kept at 900°C for 3 h, and then continuously raised to 1100-1400°C, and kept at 1100-1400°C for 4 h in an air atmosphere, and then slowly cooled to 600°C at a rate of 5°C / min, and naturally cooled to room temperature below 600°C, to obtain the final xMn 4+ :Li3LaMg2TiO7 ceramic sample.

[0037] 5) The obtained ceramic sample is irradiated with an LED light source, and 711 nm red light emission is obtained.

[0038] 6) The ceramic sample is analyzed by XRD and spectral performance, and the analysis results are shown in Figures 1-4 .

[0039] Figure 1 Fig. 2 (a-b) shows the XRD patterns of Mn 4+ ions with the highest doping concentration, i.e. x=1%, at different preparation temperatures, and it can be seen from the figure that when the temperature is higher than 1200°C, a ceramic sample with a single-phase structure can be obtained, and by analogy, other samples with lower doping concentrations will also have a single-phase structure when the preparation temperature is higher than 1200°C. Figure 1 Fig. 2 (c) is a schematic diagram of the structure of the crystal, and it can be seen that the crystal is a double perovskite structure.

[0040] Figure 2Fig. 4 (a) shows the fluorescence intensity of the internal region of samples with different concentrations at 1300℃, it can be seen that the red light emission at 711 nm reaches the maximum when the doping concentration is x = 0.2%, which means that the optimal Mn doping concentration of the fluorescent ceramic is x = 0.2%. Figure 2 Fig. 4 (c) shows the influence of different preparation temperatures on the fluorescence intensity when x = 0.2%, it can be seen that the fluorescence intensity is the largest at 1300℃, and the above information shows that 1300℃ and x = 0.2% are the optimal preparation conditions. Figure 2 Fig. 4 (b) and (d) are 3D waterfall charts respectively.

[0041] Figure 3 Fig. 4 (a) shows the fluorescence intensity of the external region of the cylinder, sphere and cuboid at 1300℃ and x = 0.2%, it can be seen from the figure that the fluorescence intensity has a strong spatial correlation, the upper surface of the cylinder has the highest efficiency, followed by the sphere surface, and the bottom of the cuboid has the lowest efficiency. Figure 3 Fig. 4 (b) is a 3D waterfall chart of (a). Figure 3 Fig. 4 (c) shows the fluorescence intensity of the upper surface of the cylinder at different temperatures, which again proves that 1300℃ is the optimal preparation temperature. Figure 3 Fig. 4 (d) is a photo of the samples with three shapes.

[0042] Figure 4 The luminescent efficiency of the samples is measured, and the samples all have the same preparation conditions, that is, the optimal preparation temperature 1300℃ and the optimal doping concentration x = 0.2%. Fig. 4 (a) is a comparison of the luminescent efficiency of the internal and external regions of the cylinder; Fig. 4 (b) is a comparison of the luminescent efficiency of the sphere and cuboid surfaces; Fig. 4 (c) is a comparison of the luminescent efficiency of the samples with three shapes; and Fig. 4 (d) is a graph of the relationship between the luminescent efficiency and the spatial distribution. It can be clearly seen from the figures that the Mn 4+ :Li3LaMg2TiO7 ceramic provided by the application has a significant spatial distribution characteristic, the upper surface of the cylinder has the highest efficiency of 93.1%, followed by the sphere surface, and the internal region of the ceramic has the lowest efficiency of only 23.6%

[0043] According to the above results, it can be found that the Mn 4+ :Li3LaMg2TiO7 ceramic provided by the application has a significant spatial distribution characteristic, which is of great significance for exploring high-efficiency fluorescent ceramics.

[0044] The above description is only the preferred embodiment of the application, and any equivalent changes and modifications made within the scope of the application are also included in the scope of the application.

Claims

1. A Mn luminous efficiency exhibiting a significant spatial distribution 4+ Activated fluorescent ceramic materials, characterized by: The Mn 4+ The chemical formula for activating fluorescent ceramic materials is xMn 4+ Li3LaMg2TiO7, where x = 0.05% ~ 1%; The luminous efficiency of Mn has a significant spatial distribution 4+ The preparation method for activated fluorescent ceramic materials includes the following preparation steps: 1) Weigh each raw material in a molar ratio of MnO2: La2O3:MgO:TiO2: Li2CO3 = x: 0.5:2: (1-x):1.5, where x = 0.05% ~ 1%; 2) Place all raw materials into an agate mortar and grind them dry until they are evenly mixed. Use distilled water as a binder to shape the materials into cylindrical, cuboid, or spherical shapes to obtain a raw blank. 3) The green blank is placed in an alumina crucible and sintered in a tube furnace at a temperature range of 1000-1300℃ for 1-8 hours, with a heating rate controlled at 5℃ / hour. Then, it is slowly cooled to room temperature to obtain the Mn. 4+ Activate fluorescent ceramic materials; Mn 4+ The activated fluorescent ceramic material is irradiated with an LED light source to obtain 711 nm red light emission, which has significant spatial distribution characteristics. The spatial distribution characteristics refer to the following: the luminous efficiency of the outer surface of the ceramic material is higher than that of the inner surface; the luminous efficiency of the upper surface of the cylindrical ceramic material is higher than that of the spherical ceramic material surface; and the luminous efficiency of the spherical ceramic material surface is higher than that of the cuboid ceramic material surface.

2. The Mn with significantly spatially distributed luminous efficiency according to claim 1 4+ Activated fluorescent ceramic materials, characterized by: The LED light source has a wavelength of 375 nm.

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