CN112625683A - Germanate type red fluorescent powder and preparation method thereof - Google Patents

Abstract

The invention discloses germanate red fluorescent powder and a preparation method thereof, wherein the general formula of the chemical composition of the germanate red fluorescent powder is Mg₃Gd_2‑xGe₃O₁₂:xEu³⁺(0<x is less than or equal to 1.0) or Mg₃Gd_2‑yGe₃O₁₂:ySm³⁺(0<y is less than or equal to 0.06) x and y are molar ratio coefficients of the doped ions, and the value ranges are as follows: 0<x≤1.0，0<y is less than or equal to 0.06. The invention has simple preparation method, easily obtained raw materials, high emission intensity and stable performance, and Eu is used³⁺Or Sm³⁺The red fluorescent powder and the existing blue and green fluorescent powder are combined to prepare the warm white LED which has high luminous brightness, good chemical stability and wider excitation and emission range, and the emission spectrum belongs to the range of orange red light, thereby meeting the requirements of the illumination field.

Description

Germanate type red fluorescent powder and preparation method thereof

Technical Field

The invention belongs to the technical field of fluorescent materials of light emitting diodes, and particularly relates to germanate type red fluorescent powder and a preparation method thereof.

Background

The energy conversion efficiency has gradually become an important index of light sources and derived products thereof, and compared with traditional light sources such as fluorescent lamps and incandescent lamps, white light LEDs have the advantages of high luminous efficiency, safety, long service life, environmental friendliness and the like, and are generally accepted green light sources. The mainstream white light LED in the market at present utilizes blue InGaN chip to excite yellow fluorescent powder YAG: Ce, and the blue light and the yellow light are mixed to obtain white light, and the method has low luminous efficiency, and is not beneficial to the requirement of indoor illumination because the color temperature is higher and the color rendering index is lower due to the lack of red light. To solve this problem, the most common method at present is to add a red component to the phosphor to increase the color rendering index and reduce the color temperature.

At present, most of commercial red powder is Eu²⁺Activated nitride or oxynitride, which needs to be reacted at high temperature and high pressure, has high requirements on the preparation process, and other sulfide red powder such as Y₂O₂S：Eu³⁺、CaS：Eu²⁺The chemical stability is poor, and the application of the red fluorescent powder is limited. Therefore, a novel red phosphor with simple method, stable physical and chemical properties and high energy conversion rate is needed, and a germanate red phosphor and a method thereof are provided for the purpose.

Disclosure of Invention

The invention aims to solve the defects of unstable physical and chemical properties and poor energy conversion rate effect in the prior art, and provides germanate red fluorescent powder and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the present invention includes a novel germanate compound Mg₃Gd₂Ge₃O₁₂Adding Eu therein³⁺And Sm³⁺The chemical composition formula is Mg₃Gd_2-xGe₃O₁₂:xEu³⁺(0<x is less than or equal to 1.0) or Mg₃Gd_2-yGe₃O₁₂:ySm³⁺(0<y≤0.06)。

A preparation method of germanate type red fluorescent powder comprises the following steps:

a is according to the formula Mg of the target compound₃Gd_2-xGe₃O₁₂:xEu³⁺Or Mg₃Gd_2-yGe₃O₁₂:ySm³⁺Wherein x is 0.1-1, y is 0.01-0.06, MgO and Gd are respectively weighed according to the stoichiometric ratio of the required metal elements₂O₃、GeO₂、Eu₂O₃(Sm₂O₃) Mixing is carried out for Mg₃Gd_2-xGe₃O₁₂:xEu³⁺Compound, MgO, Gd₂O₃、GeO₂、Eu₂O₃The mol ratio of various raw materials is 3: (1-x/2):3: x/2 for Mg₃Gd_2-yGe₃O₁₂:ySm³⁺，MgO、Gd₂O₃、GeO₂、Sm₂O₃The mol ratio of various raw materials is 3: (1-y/2) 3: y/2;

b, fully grinding the mixture to obtain a ground mixture;

c, heating the grinding mixture to 1300-1400 ℃, and sintering for 3-5 hours under the aerobic condition to obtain the blocky plate knot.

D, cooling the blocky plate knot to room temperature and grinding to obtain Eu³⁺Or Sm³⁺An ion activated garnet phosphor.

Application of germanate type red fluorescent powder in preparing white light fluorescent powder for LEDs.

An LED device comprises a fluorescent layer prepared from the germanate red fluorescent powder.

Compared with the prior art, the invention has the beneficial effects that:

the invention has simple preparation method, easily obtained raw materials, high emission intensity and stable performance, and Eu is used³⁺Or Sm³⁺The warm white LED prepared by combining the red fluorescent powder and the existing blue and green fluorescent powder has high luminous brightness, good chemical stability, wider excitation and emission range, good color rendering property, high energy conversion rate and good color temperature uniformity, can be effectively excited by near ultraviolet light or blue light emitted by a semiconductor LED chip, has an emission spectrum belonging to the range of orange red light, and can meet the requirements of the illumination field.

Drawings

FIG. 1 is an X-ray diffraction pattern and Mg of examples 2-4 and 6-8₃Y₂Ge₃O₁₂Comparison of standard card (PDF No. 89-6603);

FIG. 2 is Mg prepared in example 3 of the present invention₃Gd_1.1Ge₃O₁₂:0.9Eu³⁺An excitation spectrum obtained under the monitoring of light at 609 nm;

FIG. 3 is Mg prepared in example 3 of the present invention₃Gd_1.1Ge₃O₁₂:0.9Eu³⁺An emission spectrum obtained under 393 nanometer light excitation;

FIG. 4 is Mg prepared in example 6 of the present invention₃Gd_1.96Ge₃O₁₂:0.04Sm³⁺Excitation spectrum under 616nm optical monitoring;

FIG. 5 is Mg prepared in example 6 of the present invention₃Gd_1.96Ge₃O₁₂:0.04Sm³⁺An emission spectrum obtained under 403nm light excitation;

FIG. 6 is Mg prepared in example 3 of the present invention₃Gd_1.1Ge₃O₁₂:0.9Eu³⁺A variable temperature emission spectrum under 393 nanometer optical excitation;

FIG. 7 is Mg prepared in example 6 of the present invention₃Gd_1.96Ge₃O₁₂:0.04Sm³⁺A variable-temperature emission spectrum under 403nm light excitation;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Example 1:

according to the formula Mg₃Gd_1.3Ge₃O₁₂:0.7Eu³⁺The stoichiometric ratio of each element in (A) is 0.1524g of magnesium oxide, 0.2969g of gadolinium oxide, 0.3955g of germanium oxide and 0.1552g of europium oxide. Putting the weighed raw materials into an agate mortarThe mixture was thoroughly ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.3Ge₃O₁₂:0.7Eu³⁺And (4) red fluorescent powder.

Example 2:

according to the formula Mg₃Gd_1.2Ge₃O₁₂:0.8Eu³⁺The stoichiometric ratio of each element in the formula (I) is 0.1525g of magnesium oxide, 0.2742g of gadolinium oxide, 0.3958g of germanium oxide and 0.1775g of europium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.2Ge₃O₁₂:0.8Eu³⁺And (4) red fluorescent powder.

Example 3:

according to the formula Mg₃Gd_1.1Ge₃O₁₂:0.9Eu³⁺The stoichiometric ratio of each element in the composition is respectively 0.1526g of magnesium oxide, 0.2516g of gadolinium oxide, 0.3961g of germanium oxide and 0.1998g of europium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.1Ge₃O₁₂:0.9Eu³⁺And (4) red fluorescent powder.

Example 4:

according to the formula Mg₃Gd_1.0Ge₃O₁₂:1.0Eu³⁺The stoichiometric ratio of each element in the mixture is respectively 0.1527g of magnesium oxide, 0.2288g of gadolinium oxide and 0.3963g of germanium oxide0.2222g of europium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.0Ge₃O₁₂:1.0Eu³⁺And (4) red fluorescent powder.

Example 5:

according to the formula Mg₃Gd_1.98Ge₃O₁₂:0.02Sm³⁺The stoichiometric ratio of each element in the alloy is respectively 0.1517g of magnesium oxide, 4502g of gadolinium oxide, 0.3937g of germanium oxide and 0.0044g of samarium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.98Ge₃O₁₂:0.02Sm³⁺And (4) red fluorescent powder.

Example 6:

according to the formula Mg₃Gd_1.96Ge₃O₁₂:0.04Sm³⁺The stoichiometric ratio of each element in the raw materials is respectively 0.1517g of magnesium oxide, 0.4457g of gadolinium oxide, 0.3938g of germanium oxide and 0.0088g of samarium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.96Ge₃O₁₂:0.04Sm³⁺And (4) red fluorescent powder.

Example 7:

according to the formula Mg₃Gd_1.95Ge₃O₁₂:0.05Sm³⁺The stoichiometry of each element in (1)The weight ratio is respectively weighed as 0.1517g of magnesium oxide, 0.4435g of gadolinium oxide, 0.3939g of germanium oxide and 0.0109g of samarium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.95Ge₃O₁₂:0.05Sm³⁺And (4) red fluorescent powder.

Example 8:

according to the formula Mg₃Gd_1.94Ge₃O₁₂:0.06Sm³⁺The stoichiometric ratio of each element in the mixture is respectively 0.1517g of magnesium oxide, 0.4412g of gadolinium oxide, 0.3939g of germanium oxide and 0.0131g of samarium oxide. And the weighed raw materials are put into an agate mortar to be fully ground for 0.5 hour. Transferring the mixed material to a dried corundum crucible, putting the crucible into a tube furnace, calcining at 1350 ℃ for 4 hours, naturally cooling to room temperature along with the tube furnace to obtain white solid blocks, and grinding the blocks to obtain the final Mg₃Gd_1.94Ge₃O₁₂:0.06Sm³⁺And (4) red fluorescent powder.

As shown in fig. 2 and fig. 4, the phosphor can emit bright orange red light under the excitation of 393nm or 403nm wavelength light, can be applied to the field of LED red illumination, has high luminance, good chemical stability, wide excitation and emission range, good color rendering property, high energy conversion rate, good color temperature uniformity, and can be effectively excited by near ultraviolet light or blue light emitted by a semiconductor LED chip, and the emission spectrum belongs to the orange red light range.

As shown in FIG. 3 and FIG. 5, the phosphors prepared in examples 1 to 8 have a wavelength curve of fluorescence under the excitation of ultraviolet light, and the raw materials are slightly different, but the emission frequency band of the phosphors is stable.

FIG. 1 is an XRD diffraction pattern of example 2, example 3, example 4, example 6, example 7 and example 8, and the powder diffraction peaks of the sample are a series of independent narrow peaks with high peak intensity, which indicates that the sample has good crystallinity compared with common commercial fluorescent powder. And after high-temperature synthesis, only a target product is generated, no other impurities or byproducts are generated, and the yield is high.

FIG. 2 is a room temperature excitation spectrum (609 nm detection wavelength) of a sample in example 3, the sample has a strong excitation band in an ultraviolet region (320-400nm), and the optimal excitation wavelength is 393nm, which is very suitable for excitation of a commercial near ultraviolet chip (380-420nm), and this is also one of the advantages of the phosphor.

FIG. 3 is a graph of the room temperature emission spectra (excitation wavelength 393nm), Eu, of the samples of examples 1-4³⁺The optimal doping concentration of the ions is 0.9, the emission of the sample is a series of peaks, the strongest emission peak is about 609nm, the luminous intensity is high, the efficiency is high, and the method is suitable for the field of white light LED illumination and is used for improving the color rendering index and reducing the color temperature. Example 3 spectrum CIE coordinate value is x 0.60, y 0.38. Our sample CIE values are close to the red ntsc (national Television Standard committee) Standard (x 0.67, y 0.33).

FIG. 4 is a room temperature excitation spectrum (detection wavelength is 616nm) of the sample in example 6, the sample has a strong excitation band in the ultraviolet region (330-430nm), the optimal excitation wavelength is 403nm, and the method is also very suitable for excitation of a commercial near-ultraviolet chip (380-420 nm).

FIG. 5 is a graph of the room temperature emission spectra (excitation wavelength 403nm), Sm, of samples from examples 5-8³⁺The optimal doping concentration of the ions is 0.04, the emission of the sample is a series of peaks, the strongest emission peak is about 616nm, the luminous intensity is high, the efficiency is high, and the method is suitable for the field of white light LED illumination and is used for improving the color rendering index and reducing the color temperature. Example 7 color purity was over 85%, over the recently reported Ca₇(VO₄)₄O:7xEu³⁺(82.8%) and CaLa₂(MoO₄)₄:2xSm³⁺(78.2%) red phosphor.

FIG. 6 is a temperature-variable emission spectrum (with an excitation wavelength of 393nm) of a sample of example 3, which can maintain 65% of the room-temperature emission intensity at 423K of the white LED, is higher than that of commercial phosphor YAG (58%) and has strong thermal stability and potential application. FIG. 7 is a temperature-variable emission spectrum (excitation wavelength of 403nm) of a sample of example 6, which can maintain 72% of room-temperature emission intensity at 423K of a white LED, which is higher than that of YAG (58%) of a commercial phosphor, and has strong thermal stability and potential application.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (4)

1. A germanate type red phosphor is characterized in that Eu is added into a germanate type compound³⁺And Sm³⁺The chemical composition formula is Mg₃Gd_2-xGe₃O₁₂:xEu³⁺(0<x is less than or equal to 1.0) or Mg₃Gd_2-yGe₃O₁₂:ySm³⁺(0<y is less than or equal to 0.06), x and y are molar ratio coefficients of the doped ions, and the value range is as follows: 0<x≤1.0，0<y≤0.06。

2. A preparation method of germanate type red fluorescent powder is characterized by comprising the following steps:

the method comprises the following steps:

a is according to the formula Mg of the target compound₃Gd_2-xGe₃O₁₂:xEu³⁺Or Mg₃Gd_2-yGe₃O₁₂:ySm³⁺Wherein x is 0.1-1, y is 0.01-0.06, MgO and Gd are respectively weighed according to the stoichiometric ratio of the required metal elements₂O₃、GeO₂、Eu₂O₃(Sm₂O₃) Mixing is carried out for Mg₃Gd_2-xGe₃O₁₂:xEu³⁺Compound, MgO, Gd₂O₃、GeO₂、Eu₂O₃The mol ratio of various raw materials is 3: (1-x/2):3: x/2 for Mg₃Gd_2-yGe₃O₁₂:ySm³⁺，MgO、Gd₂O₃、GeO₂、Sm₂O₃The mol ratio of various raw materials is 3: (1-y/2) 3: y/2;

b, fully grinding the mixture to obtain a ground mixture;

c, heating the grinding mixture to 1300-1400 ℃, and sintering for 3-5 hours under the aerobic condition to obtain the blocky plate knot.

D, cooling the blocky plate knot to room temperature and grinding to obtain Eu³⁺Or Sm³⁺An ion activated garnet phosphor.

3. Use of the germanate-type red phosphor of claim 1 in the preparation of a white light phosphor for an LED.

4. An LED device comprising a phosphor layer made of the germanate-type red phosphor according to claim 1.

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