CN105670622A - Red fluorescent material for LED lamps for plant growth and preparation method of red fluorescent material - Google Patents

Abstract

The invention provides a red fluorescent material for LED lamps for plant growth and a preparation method of the red fluorescent material. The red fluorescent material is made from tetravalent manganese ion doped lithium gallium titanate and has the chemical formula as follows: LiGaTiO4:Mn<4+>, wherein the ratio of Li to Ga to Ti to Mn is 1:1:(1-x):x, and x is larger than or equal to 0.001 and smaller than or equal to 0.1. The preparation method comprises steps as follows: a raw material containing a lithium compound, a raw material containing a gallium compound, a raw material containing a titanium compound and a raw material containing a manganese compound are weighed accurately, ground, mixed uniformly and pre-sintered at the controlled temperature of 450-600 DEG C for 3-10 hours; a pre-sintered sample is taken out, ground again, mixed uniformly and sintered at the controlled high temperature of 900-1,100 DEG C for 5-10 hours; then the mixture is cooled to the room temperature with a furnace, and tetravalent manganese ion doped lithium gallium titanate is prepared. The red fluorescent material has wide ultraviolet and blue light absorption, can convert ultraviolet and blue light into red light in the spectral region of 600-780 nm efficiently and can be applied to white-light LED lighting and the red LED lamps for plant growth, and the luminescence center is 668 nm.

Description

A kind of red fluorescent material for plant growth LED lamp and preparation method thereof

technical field

The invention relates to the field of red fluorescent materials, in particular to a tetravalent manganese ion-doped gallium lithium titanate red fluorescent material for plant growth LED lamps and a preparation method thereof.

Background technique

Light environment is one of the indispensable important physical environmental factors for plant growth and development. Controlling plant morphogenesis through light quality adjustment is an important technology in the field of protected cultivation. Plant photosynthesis requires light with a wavelength of about 400-720nm, mainly through chlorophyll absorbing 440-480nm (blue) light and 640-680nm (red) for photosynthesis. LED lights have many characteristics different from other electric light sources (energy saving, environmental protection, non-toxicity, long life, etc.), and can fully meet the requirements of plant growth for red light. For example: (1) Red light can promote the rooting of chrysanthemum stems, chlorophyll formation, carbohydrate accumulation, absorption and utilization; The effects of rapid rooting and improvement of seedling quality are obvious. Plant growth red LED light is a kind of plant light, which can be applied to plant cultivation in a controllable facility environment, such as plant tissue culture, facility gardening and industrial seedling cultivation, and aerospace ecological life protection system.

The outer shell electrons of Mn ⁴⁺ ions are arranged in a d ³ structure, which can produce red to deep red luminescence in the red light region (600-750nm) under the excitation wavelength of light in the ultraviolet to blue region, so Mn ⁴⁺ Ion-doped red phosphors can be used to prepare red LEDs. In 1947, Williams et al. first discovered that Mn ⁴⁺ doped magnesium germanate emits red fluorescence; in 1960, Kemeny et al. discovered that 3.5MgO·0.5MgF ₂ ·GeO ₂ : Mn ⁴⁺ phosphor can emit red fluorescence, and 3.5MgO ·0.5MgF ₂ ·GeO ₂ : Mn ⁴⁺ phosphor became the red commercial powder on the market. At present, the practical application of the reported Mn ⁴⁺ ion-doped red phosphor in LED plant growth lamps is not very ideal, so in order to obtain qualified red LED lights for plant growth, research on new Mn ⁴⁺ ion-doped red phosphors Phosphor powder has special significance.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a new type of red fluorescent material for plant growth LED lamps. Absorbing in the blue spectral region, under the excitation of light in the ultraviolet to blue region, it has a red fluorescence covering the range of 600-780nm and a luminescent center at ~668nm, and its fluorescence has good thermal quenching characteristics.

Another object of the present invention is to provide a method for preparing the tetravalent manganese ion-doped gallium lithium titanate red fluorescent material for the above-mentioned novel plant growth LED lamp. The present invention utilizes cheap tetravalent manganese ions as active ions, and can prepare a new type of red fluorescent material for plant growth LED lamps with good thermal quenching resistance by using a high-temperature solid-phase method under relatively mild conditions and an air atmosphere.

The object of the present invention is achieved through the following technical solutions:

A new type of red fluorescent material for plant growth LED lights. The red fluorescent material is tetravalent manganese ion-doped gallium lithium titanate. Its crystal structure is orthorhombic. The chemical composition formula is LiGaTiO ₄ :Mn ⁴⁺ , and the active ion is Mn ⁴⁺ ions, element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x, where 0.001≤x≤0.1.

A method for preparing a tetravalent manganese ion-doped gallium lithium titanate red fluorescent material for a novel plant growth LED lamp, comprising the following steps:

(1) Weighing raw materials: According to the molar ratio of elements Li:Ga:Ti:Mn=1:1:(1-x):x, where 0.001≤x≤0.1, accurately weigh the compound raw materials containing lithium, containing gallium Compound raw materials, titanium-containing compound raw materials and manganese-containing compound raw materials;

(2) Pre-calcination: After grinding and mixing the raw materials weighed in step (1), pre-calcine at a temperature of 450-600°C for 3-10 hours;

(3) Firing: Take out the pre-fired sample in step (2), grind and mix again, then fire at a temperature of 900°C-1100°C for 5-10 hours, and cool to room temperature with the furnace to obtain The new plant growth LED lamp with the chemical composition LiGaTiO ₄ : Mn ⁴⁺ uses tetravalent manganese ions doped magnesium lithium niobate red fluorescent material.

The pre-firing in step (2) is carried out under air atmosphere.

The firing in step (3) is carried out under air atmosphere.

The lithium-containing compound raw material in step (1) is any one of carbonates, nitrates, chlorides, oxides, oxalates and acetates.

The gallium-containing compound raw material in step (1) is any one of carbonate, nitrate, chloride, oxide, oxalate and acetate.

The raw material of the titanium-containing compound in step (1) is any one of nitrate, chloride, oxide, oxalate and acetate.

The manganese-containing compound raw material in step (1) is any one of carbonate, nitrate, chloride, oxide, oxalate and acetate.

The red fluorescent material for novel plant growth LED lights of the present invention has the following advantages and beneficial effects:

(1) The red fluorescent material for new plant growth LED lights of the present invention is tetravalent manganese ion-doped gallium lithium titanate, which has good thermal stability, high fluorescence intensity, and good color rendering, and is a red fluorescent material with excellent performance. powder material.

(2) The new red fluorescent material for plant growth LED lamps prepared by the present invention has absorption in the (near) ultraviolet and blue spectral regions, and has a covering range of 600-780nm and a luminescent center in the range of About 668nm red fluorescence, its fluorescence has good anti-thermal quenching characteristics, the temperature has little effect on its fluorescence intensity and fluorescence lifetime, and can be applied in the fields of fluorescent lamps, solid-state LEDs and displays.

(3) The red fluorescent material based on lithium gallium titanate of the present invention is prepared in air by a high-temperature solid-phase method. The preparation method is simple and easy, does not require high temperature and high pressure conditions, and adopts a suitable and gentle heating process to obtain Red fluorescent material for plant growth LED lights with excellent performance.

Description of drawings

FIG. 1 is an excitation spectrum diagram of the novel tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in Example 1 of the present invention at an emission wavelength of 668 nm.

Fig. 2 is an emission spectrum diagram of the novel tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in Example 1 of the present invention at an excitation wavelength of 330 nm.

Fig. 3 is the emission spectrum diagrams of the novel tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in Example 1 of the present invention at excitation wavelengths of 330, 395 and 480 nm.

FIG. 4 is a time-resolved emission spectrum diagram of the novel tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in Example 1 of the present invention at an excitation wavelength of 330 nm.

Fig. 5 is the fluorescence decay curve of the novel tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in Example 1 of the present invention, the monitoring wavelength is 668nm, and the excitation wavelength is 330nm.

detailed description

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

An embodiment of the present invention provides a novel red fluorescent material for plant growth LED lamps.

Specifically, the red fluorescent material is lithium gallium titanate doped with tetravalent manganese ions, its chemical composition formula is LiGaTiO ₄ :Mn ⁴⁺ , the active ion is Mn ⁴⁺ ions, Mn ⁴⁺ ions replace Ti ⁴⁺ ions, and the element The molar ratio is Li:Ga:Ti:Mn=1:1:(1-x):x, where 0.001≤x≤0.1.

Example 1

Select lithium-containing compound raw materials, gallium-containing compound raw materials, titanium-containing compound raw materials and manganese-containing compound raw materials as starting materials, according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x) : x, respectively accurately weigh four kinds of raw materials, wherein x is respectively 0.001, 0.002, 0.004, 0.006, 0.008, 0.01, 0.12, 0.02, 0.04, 0.06, 0.08, 0.1. Four chemical raw materials of lithium carbonate, gallium oxide, titanium dioxide and manganese dioxide were weighed respectively, and the total weight of the mixture was controlled to be about 20 grams. 20 grams of the mixture was mixed by ball milling, put into a corundum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 450 ° C for 9 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 1100°C for 5 hours, and cool it to room temperature naturally with the furnace, and then you can prepare a new type of tetravalent manganese ion-doped gallium lithium titanate red fluorescent material ( LiGaTiO ₄ :Mn ⁴⁺ ); X-ray diffraction analysis shows that the prepared red fluorescent material is a pure phase of lithium gallium titanate.

The new tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) prepared in this example has excitation peaks at 330, 395 and 480 nm in the range of 200-600 nm (see Figure 1), among which, The excitation peak at 330 or 395nm matches the current commercial (near) ultraviolet chip, and the excitation peak at 480nm matches the current commercial blue light chip; the new tetravalent manganese ion-doped gallium lithium titanate red fluorescent material is about Excitation at 330, 395 and 480nm can produce red fluorescence with a peak at about 668nm, covering the 600-780nm spectral region (see Figure 2 and Figure 3); Figure 4 shows the new tetravalent manganese ion doped gallium lithium titanate red The time-resolved emission spectrum of the fluorescent material (LiGaTiO ₄ :Mn ⁴⁺ ) at an excitation wavelength of 330nm can prove that it has only one luminescent center. Figure 5 shows the fluorescence decay curve of the new tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ), the monitoring wavelength is 668nm, the excitation wavelength is 330nm, and the lifetime curve conforms to the single exponential decay equation, which is simulated The degree of agreement can reach 99.5%, and the fluorescence lifetime is about 0.189 milliseconds.

Example 2

Lithium oxide, gallium carbonate, titanium nitrate, and manganese carbonate chemicals are selected as starting materials, and the four raw materials are accurately weighed according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x , where 0.001≤x≤0.1. The total weight of the control mixture is about 20 grams. 20 grams of the mixture was mixed by ball milling, put into a corundum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 500 ° C for 8 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 1050°C for 6 hours, and cool it to room temperature with the furnace, you can prepare a new type of tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ). X-ray diffraction analysis indicated a pure phase of lithium gallium titanate. The spectral properties of the fluorescent powder and its thermal quenching resistance are similar to those in Example 1.

Example 3

Lithium nitrate, gallium chloride, titanium dioxide, and manganese carbonate chemicals are selected as starting materials, and the four raw materials are accurately weighed according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x , wherein 0.001≤x≤0.1, the total weight of the mixture is controlled to be about 20 grams. After 20 grams of the mixture were mixed by ball milling, they were put into a corundum crucible, and then the crucible was put into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 400 ° C for 10 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 1000°C for 8 hours, and cool it to room temperature with the furnace, you can prepare a new type of tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ). X-ray diffraction analysis indicated a pure phase of gallium lithium titanate. The spectral properties of the fluorescent powder and its thermal quenching resistance are similar to those in Example 1.

Example 4

Lithium oxide, gallium carbonate, titanium nitrate and manganese oxide chemicals are selected as starting materials, and the four raw materials are accurately weighed according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x , wherein 0.001≤x≤0.1, the total weight of the mixture is controlled to be about 20 grams. After 20 grams of the mixture were mixed by ball milling, they were put into a corundum crucible, and then the crucible was put into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 600 ° C for 3 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 950°C for 9 hours, and cool it to room temperature with the furnace, then you can prepare a new tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ). X-ray diffraction analysis indicated a pure phase of gallium lithium titanate. The spectral properties of the fluorescent powder and its thermal quenching resistance are similar to those in Example 1.

Example 5

Lithium carbonate, gallium carbonate, titanium nitrate and manganese carbonate chemicals are selected as starting materials, and the four raw materials are accurately weighed according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x , wherein 0.001≤x≤0.1, the total weight of the mixture is controlled to be about 20 grams. After 20 grams of the mixture were mixed by ball milling, they were put into a corundum crucible, and then the crucible was put into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 500 ° C for 5 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 900°C for 10 hours, and cool it to room temperature with the furnace, you can prepare a new tetravalent manganese ion-doped gallium lithium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ). X-ray diffraction analysis indicated a pure phase of gallium lithium titanate. The spectral properties of the fluorescent powder and its thermal quenching resistance are similar to those in Example 1.

Example 6

Lithium carbonate, gallium nitrate, titanium nitrate and manganese nitrate chemicals are selected as starting materials, and the four raw materials are accurately weighed according to the element molar ratio Li:Ga:Ti:Mn=1:1:(1-x):x , wherein 0.001≤x≤0.1, the total weight of the mixture is controlled to be about 20 grams. After 20 grams of the mixture were mixed by ball milling, they were put into a corundum crucible, and then the crucible was put into a high-temperature electric furnace. Precisely control the heating rate, control the decomposition reaction rate of the compound raw materials, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 450 ° C for 7 hours. Take out the pre-fired sample, grind and mix it again, put it into a crucible, burn it at 1100°C for 6 hours, and cool it to room temperature with the furnace, you can prepare a new type of tetravalent manganese ion-doped lithium gallium titanate red fluorescent material (LiGaTiO ₄ : Mn ⁴⁺ ). X-ray diffraction analysis indicated a pure phase of gallium lithium titanate. The spectral properties of the fluorescent powder and its thermal quenching resistance are similar to those in Example 1.

The above-mentioned examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the examples, such as: lithium-containing compound raw materials can also be (hydrogen) phosphate, acetate, etc., containing gallium Phosphate (hydrogen) salt, oxalic acid, acetate, etc., the compound raw materials containing manganese and titanium can also be hydrogen phosphate, phosphate, oxalate, acetate, etc., any other does not deviate from the spirit of the present invention Changes, modifications, substitutions, combinations, and simplifications made under the same principles shall all be equivalent replacement methods.

Claims (8)

1. A red fluorescent material for plant growth LED lamps, characterized in that the red fluorescent material is obtained by doping gallium lithium titanate with tetravalent manganese ions, its crystal structure is an orthorhombic system, and its chemical molecular formula is LiGaTiO ₄ : Mn ⁴⁺ , the active ion is Mn ⁴⁺ ion, the molar ratio of elements is: Li: Ga: Ti: Mn=1:1: (1-x): x, where 0.001≤x≤0.1. 2. A preparation method for red fluorescent material for plant growth LED lamps according to claim 1, characterized in that, comprising the following steps: (1) Weighing of raw materials: According to the molar ratio of elements Li:Ga:Ti:Mn=1:1:(1-x):x, where 0.001≤x≤0.1, accurately weigh the raw materials containing lithium compounds and the compounds containing gallium respectively Raw materials, titanium-containing compound raw materials and manganese-containing compound raw materials; (2) Pre-burning: After the raw materials weighed in step (1) are ground and mixed, they are pre-fired at a temperature of 450-600°C for 3-10 hours; (3) Firing: Take out the pre-fired sample, grind and mix again, then fire at a temperature of 900°C-1100°C for 5-10 hours, and cool to room temperature with the furnace. 3. The preparation method of the red fluorescent material for plant growth LED lamps according to claim 2, characterized in that, the pre-burning is carried out in an air atmosphere. 4. The preparation method of the red fluorescent material for plant growth LED lamps according to claim 2, characterized in that, the firing is carried out in an air atmosphere. 5. the preparation method of red fluorescent material for plant growth LED lamp according to claim 2, is characterized in that, described lithium-containing compound raw material is carbonate, nitrate, chloride, oxide compound, oxalate and vinegar any of the salts. 6. the preparation method of red fluorescent material for plant growth LED lamp according to claim 2, is characterized in that, described gallium-containing compound raw material is carbonate, nitrate, chloride, oxide compound, oxalate and vinegar any of the salts. 7. the preparation method of red fluorescent material for plant growth LED lamp according to claim 2, is characterized in that, described titanium-containing compound raw material is in nitrate, chloride, oxide compound, oxalate and acetate any kind. 8. the preparation method of red fluorescent material for plant growth LED lamp according to claim 2, is characterized in that, described manganese-containing compound raw material is oxide salt, chloride, carbonate, oxalate, acetate and any of the nitrates.