CN101649199B - Ultraviolet light stimulated phosphor - Google Patents

Abstract

A white light phosphor excited by ultraviolet light, which is composed of the following raw materials: (1) one or a combination of CaCO ₃ and Ca(HCO ₃ ) ₂ ; (2) one of MoO ₃ and WO ₃ ; (3) Pr ₆ O ₁₁ ; Ingredient distribution ratio: the molar concentration of Pr ions and Ca ions is equal to the molar concentration of W or Mo ions, and the molar ratio of Pr ions to W or Mo ions is less than 0.03, greater than 0.01, including 0.01 and 0.03. The preparation method of white light phosphor has three steps: Step 1: Weigh high-purity reagents CaCO ₃ , Ca(HCO ₃ ) ₂ , MoO ₃ , WO ₃ , Pr ₆ O ₁₁ according to the stoichiometric ratio and mix them uniformly; Step 2: Mix them Grind in an agate mortar or ball mill for 1-3 hours, then put it into a corundum crucible and sinter at a high temperature for 2-5 hours, the sintering temperature is 700-1200°C; Grind in a ball mill for 1-2 hours. The invention uses a high-temperature solid-phase synthesis method to obtain a single-component fluorescent powder with stable chemical properties, which emits warm white light with a low color temperature (3000-4000K) under the excitation of ultraviolet light, and has wide practical value and application prospect.

Description

A white light phosphor excited by ultraviolet light

(1) Technical field

The invention relates to a white light phosphor excited by ultraviolet light. The white light phosphor is a phosphor material capable of converting ultraviolet (UV) rays into white light, and belongs to the technical field of optoelectronic chemistry.

(2) Background technology

Fluorescent materials absorb energy in one region of the electromagnetic spectrum and emit radiant energy in another region of the spectrum. Powdered fluorescent materials are usually called phosphors, and transparent solid fluorescent materials are usually called scintillators.

There are two types of well-known fluorescent materials: self-excited fluorescent materials and impurity-activated fluorescent materials.

A self-excited fluorescent material is a pure crystalline host material that raises electrons to an active state when it absorbs a high-energy photon, and returns from this active state to a lower-energy state by emitting a photon. Self-excited fluorescent materials have a wide spectral emission pattern due to the wide energy range of electrons in the active state or low energy state. Therefore, the excited electrons emit photons with a wide energy range during the transition from the excited state to the low-energy state, and the emitted photon energy is related to the specific energy before and after the transition of the electron emission state.

The matrix of impurity-activated fluorescent materials is usually a non-fluorescent main material, which is modified by adding a low concentration of activator. For impurity-activated fluorescent materials, the activator ions can directly absorb the incident photons or transfer them to the activated ions after being absorbed by the crystal lattice, so that the electrons of the activated ions are promoted to an excited state. These electrons emit fluorescent photons when returned to a lower energy state.

White light-emitting diodes (LEDs) are widely used in the field of lighting due to their significant advantages such as high efficiency, low power consumption, long life, solid-state energy saving, and environmental protection. At present, there are three main methods of using LED technology to realize white light: the direct color mixing method of three primary color LEDs, the ultraviolet conversion method, and the method of adding yellow phosphor powder to blue light chips.

(1) Tricolor LED color mixing method

The three-primary-color chips that emit red, green, and blue wavelengths are directly packaged together to form a multi-chip white light LED. Through the principle of spatial color mixing, they are matched according to an appropriate ratio, so that the light of the three colors is mixed into white light. The disadvantage of this method is that its installation structure is relatively complicated, and the driving voltage, luminous efficiency, and light distribution characteristics of LEDs of various colors are different, and the intensity of the three primary colors of red, green, and blue needs to be adjusted by current, and the circuit implementation is more complicated. At the same time, because LEDs of different colors have different aging characteristics over time, resulting in differences in light decay. Therefore, the pre-adjusted white light will change color during use due to the difference in light attenuation of different colors, which makes the mixed white light less stable and has differences in temperature characteristics. All the light comes from light-emitting diodes, and the relative cost is relatively high.

(2) The method of ultraviolet conversion

With LED as the basic light source, the ultraviolet light emitted by the LED is used to excite the fluorescent material, and the wavelength conversion is realized by the phosphor powder to emit visible light. Finally, all the light used for illumination comes from the fluorescent material, and the excitation spectrum of the fluorescent material is required to match the emission spectrum of the LED, so that a higher light conversion efficiency can be obtained. The fluorescent material can be a combination of various fluorescent powders, that is, white light is produced by mixing different colors of light, or it can be a single fluorescent powder that can emit white light.

(3) The method of adding yellow phosphor powder to the blue light chip

The light emission of GaN-based blue LED with a wavelength of 460-470nm is used as the basic light source. Part of the blue light emitted by it is used to excite the phosphor powder, so that the phosphor powder emits yellow-green light; the other part of the blue light is emitted through the phosphor powder, and the yellow-green light emitted by the phosphor powder is mixed with the transmitted part of the GaN-based blue LED to form white light. That is, the mechanism of white light=blue+yellow. Its disadvantage is that the color rendering is worse, which is mainly due to the less red component in the emission spectrum. To make up for this deficiency, red phosphor powder is usually added to the phosphor powder to obtain warm white light with a lower color temperature. Since this method needs to be mixed with red phosphors to produce warm white light, the process is more difficult, and most of the red phosphors currently used are deliquescent sulfides and fluorides, resulting in poor luminescence stability.

Therefore, we provide a single-component fluorescent material with stable chemical properties, which can emit warm white light with a low color temperature under the excitation of a single excitation source without mixing multiple fluorescent materials.

(3) Contents of the invention

1. Purpose: The purpose of the present invention is to provide a white light phosphor excited by ultraviolet light, which can obtain a single-component white light phosphor without mixing a variety of fluorescent materials, that is, to obtain a single-component fluorescent material that can provide White light lighting system, and under the excitation of a single excitation source, the lighting system can emit warm white light with low color temperature.

2. Technical solution:

The present invention is a white light phosphor excited by ultraviolet light, which is composed of the following raw materials:

(1) One or a combination of CaCO ₃ (analytical pure), Ca(HCO ₃ ) ₂ (analytical pure)

(2) One of MoO ₃ (analytical pure), WO ₃ (analytical pure)

(3) Pr ₆ O ₁₁ (purity 99.99%)

Its stoichiometric composition ratio is: the molar concentration of Pr ion and Ca ion is equal to the molar concentration of W or Mo ion, and the molar ratio of Pr ion to W or Mo ion is less than 0.03, greater than 0.01, including 0.01 and 0.03.

n(Pr)+n(Ca)=n(W) Among them, 0.01≤n(Pr)/n(W)≤0.03

Or n(Pr)+n(Ca)=n(Mo) Among them, 0.01≤n(Pr)/n(Mo)≤0.03

The molecular formula of the white phosphor is Ca _1-x Pr _x MO ₄ , M is one of molybdenum or tungsten, and the value of X is preferably between 0.01 and 0.03, including 0.01 and 0.03. The white light phosphor is synthesized to have a scheelite structure without a main structure doped with rare earths. Tungstates and molybdates are self-excited materials with unique broad-spectrum emission patterns. Primary absorption generally occurs at wavelengths less than 350 nm. The host lattice absorption is caused by tungstate-based [WO ₄ ] ^2- or molybdate-based [MoO ₄ ] ^2- . In the case of the main structure of scheelite and the excitation of UV rays, the emission spectrum of the main structure is a broad band centered around 540nm. The fluorescent material doped with praseodymium ions is a self-excited material that provides a luminescent main structure, and is also an impurity-activated luminescent material. The emission spectrum emitted by the fluorescent material includes not only the broadband emission emitted from the host lattice structure, but also the narrow-band emission emitted by the rare earth impurity activator. To prepare Ca _1-x Pr _x MoO ₄ , calcium carbonate (CaCO ₃ ), calcium bicarbonate (Ca(HCO ₃ ) ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), molybdenum oxide (MoO ₃ ) and oxide Tungsten (WO ₃ ) etc. are uniformly mixed according to the above ideal ratio.

The primary structure acts as an activator, which absorbs the activation energy from the UV source and transfers this energy to the praseodymium ions, which emit the corresponding energy in the form of optical radiation. Figure 3 shows the emission spectrum of Ca _1-x Pr _x MoO ₄ under the excitation of UV rays at 325nm, where the value of x is equal to 0.02. Line-shaped emission at 489nm, 604nm and 651nm, derived from the stimulated emission of Pr ³⁺ , 540nm The left and right broadband luminescence is the luminescence of the CaMO ₄ main structure. The color coordinates (x=0.41, y=0.39) of this emitted light on the CIE color chart correspond to a color temperature of 3450K. When the concentration of Pr in the fluorescent material deviates from x=0.02, the color coordinates of the light emitted by the fluorescent material will change, but as long as it is in the range of 0.01 to 0.03, white light can still be obtained even if the color temperature of the emitted light changes. In this way, a range of white light with different color temperatures can be obtained from a single component material.

A kind of preparation method of the white light fluorescent powder excited by ultraviolet light of the present invention, its specific steps are as follows:

Step 1: Weigh high-purity reagents CaCO ₃ , Ca(HCO ₃ ) ₂ , MoO ₃ , WO ₃ , and Pr ₆ O ₁₁ , and mix them evenly according to the stoichiometric ratio, which is: Pr ions and Ca ions in moles The concentration sum is equal to the molar concentration of W or Mo ions, and the molar ratio of Pr ions to W or Mo ions is less than 0.03 and greater than 0.01, including 0.01 and 0.03;

Step 2: Grind them in an agate mortar or ball mill for 1-3 hours to mix them evenly, put the above mixture into a corundum crucible, and place it in a high-temperature furnace for sintering, the atmosphere is air or nitrogen, and the sintering temperature is 700- 1200°C, the sintering time is 2-5 hours; the obtained in this step is the sintered product with the molecular formula Ca _1-x Pr _x MO ₄ ;

Step 3: The sintered product is lowered to room temperature in the air, and ground again in an agate mortar or ball mill for 1-2 hours to obtain the desired product—white phosphor powder.

3. Advantages and effects of the present invention: a white light phosphor excited by ultraviolet light of the present invention, compared with the prior art, has the advantage of obtaining a white light phosphor by a solid phase reaction, thereby, it can be used in a single Under the excitation of the ultraviolet excitation source, the chemically stable single-component phosphor absorbs ultraviolet rays and emits white light. It does not need to mix a variety of fluorescent materials to obtain warm white light with a low color temperature (3000-4000K).

(4) Description of drawings

Fig. 1 schematic diagram of lighting system of the present invention

Fig. 2 schematic diagram of excitation spectrum of fluorescent material of the present invention

Figure 3 is a schematic diagram of the emission spectrum of the fluorescent material of the present invention under excitation at 325nm

The color coordinate schematic diagram of Fig. 4 fluorescent material of the present invention

Fig. 5 schematic flow chart of the preparation method of white light phosphor of the present invention

The symbols in Figure 1 are explained as follows:

1 radiation source; 2 ultraviolet light; 3 fluorescent material; 4 fluorescent.

(5) Specific implementation methods

The present invention is a white light phosphor excited by ultraviolet light, which is composed of the following raw materials:

(1) One or a combination of CaCO ₃ (analytical pure), Ca(HCO ₃ ) ₂ (analytical pure)

(2) One of MoO ₃ (analytical pure), WO ₃ (analytical pure)

(3) Pr ₆ O ₁₁ (purity 99.99%)

Its stoichiometric composition ratio is: the molar concentration of Pr ion and Ca ion is equal to the molar concentration of W or Mo ion, and the molar ratio of Pr ion to W or Mo ion is less than 0.03, greater than 0.01, including 0.01 and 0.03.

n(Pr)+n(Ca)=n(W) Among them, 0.01≤n(Pr)/n(W)≤0.03

Or n(Pr)+n(Ca)=n(Mo) Among them, 00.01≤n(Pr)/n(Mo)≤0.03

The present invention is a method for preparing a white light phosphor excited by ultraviolet light. The specific implementation steps of the method are listed as follows:

Example 1:

Step 1: Weigh high-purity reagents CaCO ₃ (analytical pure), MoO ₃ (analytical pure), Pr ₆ O ₁₁ (purity 99.99%), and their molar ratios are as follows:

n(CaCO ₃ ):n(Pr ₆ O ₁₁ ):n(MoO ₃ )=594:1:600;

Step 2: Grind them in an agate mortar for 1 hour to make them evenly mixed, put the above mixture into a corundum crucible, and place it in a high-temperature furnace for sintering, the atmosphere is air, the sintering temperature is 800°C, and the sintering time is 2 hours ;

Step 3: The sintered product was lowered to room temperature in the air, and ground again in an agate mortar for 1 hour to obtain the desired product. A kind of white light fluorescent powder excited by ultraviolet light is obtained, and the sample is light yellow powder. The excitation band is less than 350nm. When the sample is excited at 325nm, there are emission peaks around 498nm, 600nm and 650nm, and there is broadband luminescence around 540nm.

Example 2:

Step 1: Weigh high-purity reagents CaCO ₃ (analytical pure), WO ₃ (analytical pure), Pr ₆ O ₁₁ (purity 99.99%), and their molar ratios are as follows:

n(CaCO ₃ ):n(Pr ₆ O ₁₁ ):n(WO ₃ )=294:1:300;

Step 2: Grind them in an agate mortar for 1 hour to make them evenly mixed, put the above mixture into a corundum crucible, and place it in a high-temperature furnace for sintering, the atmosphere is air, the sintering temperature is 800°C, and the sintering time is 2 hours ;

Step 3: The sintered product was lowered to room temperature in the air, and ground again in an agate mortar for 1 hour to obtain the desired product. A kind of white light fluorescent powder excited by ultraviolet light is obtained, and the sample is light yellow powder. The excitation band is less than 350nm. When the sample is excited at 325nm, there are emission peaks around 498nm, 600nm and 650nm, and there is broadband luminescence around 530nm.

The fluorescent powders obtained in the above two examples are powdery crystals, soluble in inorganic acids, but insoluble in ethanol, ether or water. The lighting system provided by the present invention is obtained by coating the obtained fluorescent powder on a suitable substrate, such as an LED or a lamp tube capable of emitting UV rays.

See Figure 1, a white light phosphor white light lighting system excited by ultraviolet light, which is composed of a radiation source 1 and a fluorescent material 3, the radiation source 1 emits a ray 2 to the fluorescent material 3, and the fluorescent material 3 absorbs the light that excites it UV rays that fluoresce in the visible range of the spectrum4.

Wherein, the radiation source 1 is a light emitting diode (LED), and the radiation emitted by the radiation source 1 is 325nm ultraviolet rays. Wherein, the fluorescent material 3 is white light fluorescent powder Ca _1-x Pr _x MoO ₄ , and the value of x is equal to 0.02.

Fig. 2 is a schematic diagram of the excitation spectrum of _the white light phosphor of the present invention; Fig. 3 shows the emission spectrum of Ca _1-x Pr _x MoO under the excitation of 325nm UV rays, wherein the x value is equal to 0.02; Fig. 4 is the color of the white light phosphor of the present invention Coordinate schematic diagram, Fig. 5 is a block schematic diagram of the process flow of the white light phosphor preparation method of the present invention.

Claims (2)

1. A method for preparing white light fluorescent powder excited by ultraviolet light, characterized in that: the specific steps of the method are as follows: Step 1: Weigh high-purity reagents CaCO ₃ , MoO ₃ , and Pr ₆ O ₁₁ , and their molar ratios are as follows: n(CaCO ₃ ):n(Pr ₆ O ₁₁ ):n(MoO ₃ )=594:1:600; CaCO ₃ and MoO ₃ are analytically pure; the purity of Pr ₆ O ₁₁ is 99.99%; Step 2: Grind them in an agate mortar for 1 hour to make them evenly mixed, put the above mixture into a corundum crucible, and place it in a high-temperature furnace for sintering, the atmosphere is air, the sintering temperature is 800°C, and the sintering time is 2 hours ; Step 3: Lower the sintered product to room temperature in the air, and grind it again in an agate mortar for 1 hour to obtain the desired product; a kind of ultraviolet-excited white light phosphor is obtained, and the sample is light yellow powder; the excitation band is less than 350nm; When the sample is excited at 325nm, there are emission peaks around 498nm, 600nm and 650nm, and there is broadband light emission near 540nm; the obtained phosphor is powdery crystal, soluble in inorganic acid, insoluble in ethanol, ether or water. 2. A preparation method of white light phosphor excited by ultraviolet light, characterized in that: the specific steps of the method are as follows: Step 1: Weigh high-purity reagents CaCO ₃ , WO ₃ , and Pr ₆ O ₁₁ , and their molar ratios are as follows: n(CaCO ₃ ):n(Pr ₆ O ₁₁ ):n(WO ₃ )=294:1:300; CaCO ₃ and WO ₃ are analytically pure; the purity of Pr ₆ O ₁₁ is 99.99%; Step 2: Grind them in an agate mortar for 1 hour to make them evenly mixed, put the above mixture into a corundum crucible, and place it in a high-temperature furnace for sintering, the atmosphere is air, the sintering temperature is 800°C, and the sintering time is 2 hours ; Step 3: Lower the sintered product to room temperature in the air, and grind it again in an agate mortar for 1 hour to obtain the desired product; a kind of ultraviolet-excited white light phosphor is obtained, and the sample is light yellow powder; the excitation band is less than 350nm; When the sample is excited at 325nm, there are emission peaks around 498nm, 600nm and 650nm, and there is broadband light emission near 530nm; the obtained phosphor is powdery crystal, soluble in inorganic acid, insoluble in ethanol, ether or water.

Images