CN111944526A - Manganese ion-doped gallate red fluorescent material for white light LED and preparation method thereof - Google Patents

Abstract

_The invention provides a _gallate red ^fluorescent material doped with manganese ions for white light LED and a preparation method thereof. The active ion is Mn ⁴⁺ . The method includes weighing a certain amount of compound raw materials containing strontium, lanthanum, gallium and manganese, grinding and mixing, pre-burning at 400-600 DEG C for 2-4 hours in an oxidizing atmosphere, taking out, grinding and mixing at 650 °C in an oxidizing atmosphere calcined at ~950°C for 2-4 hours, then taken out, ground and mixed, and fired at 1100-1300°C for 4-8 hours in an oxidizing atmosphere to obtain a red fluorescent material. The emission intensity of the red fluorescent material prepared by the invention shows a trend of first increasing and then decreasing with the increase of the doping ion concentration, the fluorescent powder has broad near-ultraviolet and blue-light absorption, and has a coverage of 650-780 nm under near-ultraviolet or blue light excitation interval of red fluorescence.

Description

Manganese ion-doped gallate red fluorescent material for white light LED and preparation method thereof

technical field

The invention relates to the technical field of fluorescent materials, in particular to a manganese ion-doped gallate red fluorescent material for white light LEDs and a preparation method thereof.

Background technique

As a green light source in the 21st century, white LEDs have a series of advantages compared with traditional light sources, such as high efficiency, energy saving, green environmental protection, long life, and not easy to be damaged. Applications.

At present, LED chips and phosphors are mainly used to obtain white light LEDs (hereinafter referred to as WLEDs). The simplest one is to combine InGaN blue LED chips (usually emitting wavelengths of 450-480 nm) with Ce ³⁺ ions doped with blue light absorption. The combination of yttrium aluminum garnet (Y3Al5O12:Ce ³⁺ ) yellow phosphors, this combination of InGaN blue LED chips and Y3Al5O12:Ce ³⁺ (hereinafter referred to as BLED+YAG:Ce) has been commercialized. However, due to the lack of red luminescent components in the white light obtained in this way, there are disadvantages such as high color temperature (usually at 4500-6500K) and low color rendering index (usually less than 80).

In order to solve this problem, a red fluorescent material that can be effectively excited by blue light can be introduced into commercial WLEDs, or an LED chip with near-ultraviolet light (350-410nm) can be used to excite a mixed phosphor of red, blue and green to make a fluorescent powder. WLED. Among them, both solutions require the development of highly efficient red fluorescent materials that can be excited by near-ultraviolet or blue light.

The dependence of the white LED market on red fluorescent materials has promoted the development of new red fluorescent materials. Some rare earth and transition metal ion-doped inorganic compounds or quantum dots and other luminescent materials have been reported continuously. Among them, the red fluorescent materials doped with rare earth Eu ³⁺ , Sm ³⁺ and Pr ³⁺ ions have linear absorption bands in the near-ultraviolet region and blue light region due to the limitation of energy level transitions, and the peak widths are mostly less than 10 nm, which is higher than that of LEDs. The emission band of the chip is much narrower, so that only a part of the light emitted from the LED chip can be used, thereby reducing the overall efficiency of the LED device. At the same time, the leakage of near-ultraviolet light will cause near-ultraviolet radiation, which is also harmful to human health during lighting. harm.

Currently, ^Eu doped nitride and oxynitride phosphors have attracted much attention due to their excellent luminescence properties and are considered to be the most promising phosphors. Its quantum efficiency exceeds 70%, but this type of phosphor needs to be synthesized under high temperature and high pressure conditions. For example, the red fluorescent material CaAlSiN3:Eu ²⁺ needs to be synthesized at 1800°C, 10 atmospheres and nitrogen atmosphere. Harsh preparation process conditions and high raw material prices hinder their commercialization process; and these Eu ²⁺ ion-doped phosphors with blue light absorption also have strong absorption in the green region, so they will absorb all the characteristics of white LEDs. The green part of the white light emitted reduces the overall device efficiency. In conclusion, the nature of the fd transition of rare earth ions determines that rare earth phosphors cannot fundamentally overcome these drawbacks, so it is crucial to seek suitable luminescent ions.

The luminescent materials doped with excessive metal Mn ⁴⁺ ions can also emit red light under near-ultraviolet or blue light excitation, which has positive significance for reducing the over-reliance on expensive rare earth materials in the optoelectronic field. At present, the research on this type of materials mainly focuses on Mn ⁴⁺ doped fluorides, such as KTiF ₆ : Mn ⁴⁺ red fluorescent material reported by Setlur et al. The warm white LED device prepared with it has an efficiency of 85%. , the color rendering index is 90, and the color temperature is 3088K, which is far better than the combination of BLED+YAG:Ce. However, from the perspective of environmental protection, the preparation of fluoride requires the use of hydrofluoric acid, which is extremely harmful to the environment. From the perspective of chemical stability, fluoride has poor stability in normal environments. The one that has been commercialized is 3.5MgO.0.5MgF ₂ .GeO ₂ :Mn ⁴⁺ , the emission peak is located at 658 nm, and the excitation spectrum is located at 230-450 nm, which is limited due to its lack of obvious absorption in the blue light region (450-480 nm). Scope of application.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the present invention provides a manganese ion-doped gallate red fluorescent material for a white light LED and a preparation method thereof.

The technical scheme of the present invention is as follows: a gallate red fluorescent material doped with manganese ions for a white light LED, the material uses Mn to replace Ga in the crystal, its crystal structure belongs to the orthorhombic system, and the chemical composition molecular formula is SrLaGa ₃ O ₇ :Mn ^{4 +} , the active ion is Mn ⁴⁺ , and the element molar ratio is Sr:La:Ga:Mn=1:1:3(1-x):3x, where 0≤x<0.1.

The invention also provides a preparation method of a manganese ion-doped gallate red fluorescent material for a white light LED, comprising the following steps:

S1), by element molar ratio Sr:La:Ga:Mn=1:1:3(1-x):3x, wherein 0≤x<0.1; Weigh the compound raw materials containing strontium, lanthanum, gallium and manganese respectively;

S2), grind and mix the compound raw materials weighed in step S1) and pre-fire in an oxidizing atmosphere, the temperature is 400～600 ℃, and the time is 2～4 hours;

S3), take out the sample after the pre-burning in step S2), grind and mix well and burn in an oxidizing atmosphere, the temperature is 650≤T≤950°C, and the time is 2≤t≤4 hours;

S4), taking out the sample after burning in step S3), grinding and mixing, and burning in an oxidizing atmosphere again, the temperature is 1100-1300 ° C, and the time is 4≤t≤8 hours to obtain manganese-doped gallate red fluorescent material.

Preferably, in step S1), the strontium-containing compound raw material is any one of strontium carbonate and strontium nitrate.

Preferably, in step S1), the raw material of the lanthanum-containing compound is lanthanum oxide.

Preferably, in step S1), the gallium-containing compound raw material is any one of gallium oxide, gallium nitrate and gallium hydroxide.

Preferably, in step S1), the manganese-containing compound raw material is any one of manganese oxide, manganese oxide, manganese dioxide and manganese carbonate.

Preferably, in step S1), the x=0.001, T=1200°C, and t=5h.

Preferably, in step S2), the oxidizing atmosphere is an air atmosphere or an oxygen atmosphere.

Preferably, the fluorescent material emits red light under the excitation of near-ultraviolet light or blue light, emits light in the range of 650-780 nm, and has two light-emitting centers at 691 nm and 715 nm.

The beneficial effects of the present invention are:

1. The phosphor powder prepared by the present invention has absorption in the near-ultraviolet and blue-light spectral regions, and under the excitation of light in the near-ultraviolet to blue light region (250-500nm), it has a red color covering the range of 650-780nm and the emission center at 691nm and 714nm. Fluorescence can be used in fluorescent lamps, solid-state LEDs and displays;

2. The fluorescent powder prepared by the present invention is a red fluorescent material with SrLaGa ₃ O ₇ as a matrix, and is prepared in the air by a high-temperature solid-phase method. A manganese ion-doped gallate red fluorescent material for white LED with excellent performance is obtained;

3. The fluorescent powder prepared by the present invention does not use rare earth ions as the luminescent center, and uses cheap manganese as an activator to control its valence to +4 to obtain a red luminescent material;

4. The raw materials used for the fluorescent powder prepared by the present invention are simple, no harmful substances will be produced during the preparation process, and no harm to the environment;

5. The phosphor powder prepared by the invention has stable structure, simple synthesis method, convenient large-scale production, and can be widely used in near-ultraviolet-near-ultraviolet LED chip white light LED devices.

Description of drawings

Fig. 1 is the X-ray powder diffraction pattern of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ prepared by the ratios (1)-(6) of Example 1 of the present invention;

Fig. 2 is the excitation spectrum diagram of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ prepared by the ratios (1)-(6) of Example 1 of the present invention at a monitoring wavelength of 715 nm;

3 is an emission spectrum diagram of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared by the ratios (1)-(6) of Example 1 of the present invention at an excitation wavelength of 380 nm.

4 is an emission spectrum diagram of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared by the ratios (1)-(6) of Example 1 of the present invention at different temperatures at a monitoring wavelength of 715 nm.

5 is the relationship between the temperature and the spectral intensity of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared in Example 1 of the present invention.

FIG. 6 is the fluorescence decay curve of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared in Example 1 of the present invention at an excitation wavelength of 370 nm.

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings:

Example 1

A preparation method of a manganese ion-doped gallate red fluorescent material for a white light LED, comprising the following steps:

S1), select strontium carbonate, lanthanum oxide, gallium oxide and manganese dioxide as starting compound raw materials, according to the molar ratio of each element, take by weighing four kinds of compound raw materials respectively, a total of 6 groups, the proportions are as follows:

(1) Sr:La:Ga:Mn=1:1:3:0, corresponding to x=0;

(2) Sr:La:Ga:Mn=1:1:2.997:0.003, corresponding to x=0.001;

(3) Sr:La:Ga:Mn=1:1:2.991:0.009, corresponding to x=0.003;

(4) Sr:La:Ga:Mn=1:1:2.985:0.015, corresponding to x=0.005;

(5) Sr:La:Ga:Mn=1:1:2.97:0.03, corresponding to x=0.01;

(6) Sr:La:Ga:Mn=1:1:2.7:0.3, corresponding to x=0.1;

S2), the total weight of the control mixture is 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; the heating rate is precisely controlled, and the compound raw material decomposition reaction speed is controlled to prevent the mixture After overflowing from the crucible, the mixture was calcined at 1200 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain the target material, that is, Mn ⁴⁺ ion-doped gallate red fluorescent material for new white LEDs; X-ray Diffraction analysis showed that the prepared red fluorescent material was SrLaGa ₃ O ₇ crystal phase.

FIG. 1 is the powder X-ray diffraction spectrum of the samples of the proportions (1)-(5) of this embodiment. The radiation source is Cu target Kα ray, the test voltage is 40kV, the test current is 40mA, the scanning step is 0.02°/step, and the scanning speed is 0.12s/step. XRD pattern analysis shows that the phase of the sample obtained at 1200 ℃ is SrLaGa ₃ O ₇ phase, which belongs to the orthorhombic system, and the doping of manganese has no effect on the formation of the crystal phase.

FIG. 2 is an excitation spectrum diagram of the samples of the ratios (1)-(5) of this embodiment, and the monitoring wavelength is 715 nm. Measured by FLS980 steady-state transient fluorescence spectrometer from Edinburgh, UK. A 450W xenon lamp was used as the light source, equipped with a time-corrected single photon counting card (TCSPC), a thermoelectric cold red sensitive photomultiplier tube (PMT), a TM300 excitation monochromator and a dual TM300 emission monochromator. It can be seen from FIG. 2 that the excitation spectrum of the red fluorescent material prepared in this embodiment covers light in the spectrum of 220-550 nm, which matches with the near-ultraviolet and blue-light chips currently commercialized.

FIG. 3 is an emission spectrum diagram of the samples of the ratios (1)-(6) of this embodiment, and the excitation wavelength is 380 nm. The target material can be generated by excitation by near-ultraviolet or blue light, covering the 650-780 nm spectral region. It can be seen from Fig. 3 that the red emission of the sample under the excitation of near-ultraviolet light or blue light covers the spectral region of 650-750 nm, corresponding to the ² E→ ⁴ A ₂ transition, and has two emission centers at 691 nm and 715 nm.

FIG. 4 is an emission spectrum diagram of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared by the ratios (1)-(6) of the embodiment at different temperatures at a monitoring wavelength of 715 nm.

FIG. 5 is the relationship between the temperature and the spectral intensity of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared in Example 1. FIG.

FIG. 6 is the fluorescence decay curve of the red fluorescent material SrLaGa ₃ O ₇ : Mn ⁴⁺ sample prepared in this example at an excitation wavelength of 370 nm.

Example 2

This embodiment provides a method for preparing a manganese ion-doped gallate red fluorescent material for a white light LED, including the following steps:

S1), select the raw material containing strontium carbonate, lanthanum oxide, gallium oxide, manganese dioxide as starting material, according to element mole Sr:La:Ga:Mn=1:1:3(1-x):3x, corresponding to x= 0.001, respectively accurately weigh the four raw materials,

S2), control the total weight of the mixture at 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; precise control of the heating rate, control of the compound raw material decomposition reaction speed, to prevent the mixture from The crucible overflowed, the mixture was calcined at 1100 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain a new type of white light LED Mn ⁴⁺ ion-doped gallate red fluorescent material; X-ray diffraction analysis showed that the prepared The red fluorescent material is SrLaGa ₃ O ₇ crystal phase.

Example 3

This embodiment provides a method for preparing a manganese ion-doped gallate red fluorescent material for a white light LED, including the following steps:

S1), select the raw material containing strontium carbonate, lanthanum oxide, gallium oxide, manganese dioxide as starting material, according to element mole Sr:La:Ga:Mn=1:1:3(1-x):3x, corresponding to x= 0.001, respectively accurately weigh the raw materials,

S2) control the total weight of the mixture to be 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; the heating rate is precisely controlled, and the decomposition reaction rate of the compound raw materials is controlled to prevent the mixture from being released from the crucible. The mixture was calcined at 1150 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain a new type of white light LED Mn ⁴⁺ ion-doped gallate red fluorescent material; X-ray diffraction analysis showed that the prepared red fluorescent material The fluorescent material is SrLaGa ₃ O ₇ crystal phase; the spectral properties of the fluorescent powder are similar to those of Example 1.

Example 4

This embodiment provides a method for preparing a manganese ion-doped gallate red fluorescent material for a white light LED, including the following steps:

S1), select the raw material containing strontium carbonate, lanthanum oxide, gallium oxide, manganese dioxide as starting material, according to element mole Sr:La:Ga:Mn=1:1:3(1-x):3x, corresponding to x= 0.001, respectively accurately weigh the raw materials,

S2), control the total weight of the mixture at 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; precise control of the heating rate, control of the compound raw material decomposition reaction speed, to prevent the mixture from The crucible overflowed, the mixture was calcined at 1200 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain a new type of white light LED Mn ⁴⁺ ion-doped gallate red fluorescent material; X-ray diffraction analysis showed that the prepared The red fluorescent material is SrLaGa ₃ O ₇ crystal phase; the spectral properties of the fluorescent powder are similar to those of Example 1.

Example 5

This embodiment provides a method for preparing a manganese ion-doped gallate red fluorescent material for a white light LED, including the following steps:

S1), select the raw material containing strontium carbonate, lanthanum oxide, gallium oxide, manganese dioxide as starting material, according to element mole Sr:La:Ga:Mn=1:1:3(1-x):3x, corresponding to x= 0.001, respectively accurately weigh the raw materials;

S2), control the total weight of the mixture at 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; the heating rate is precisely controlled, and the compound raw material decomposition reaction speed is controlled to prevent the mixture from The crucible overflowed, the mixture was calcined at 1250 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain a new type of white light LED Mn ⁴⁺ ion-doped gallate red fluorescent material; X-ray diffraction analysis showed that the prepared The red fluorescent material is SrLaGa ₃ O ₇ crystal phase; the spectral properties of the fluorescent powder are similar to those of Example 1.

Example 6

This embodiment provides a method for preparing a manganese ion-doped gallate red fluorescent material for a white light LED, including the following steps:

S1), select the raw material containing strontium carbonate, lanthanum oxide, gallium oxide, manganese dioxide as starting material, according to element mole Sr:La:Ga:Mn=1:1:3(1-x):3x, corresponding to x= 0.001, respectively accurately weigh the raw materials;

S2), control the total weight of the mixture at 5 grams; 5 grams of the mixture is put into a corundum crucible after grinding and mixing, and then the crucible is put into a high-temperature electric furnace; precise control of the heating rate, control of the compound raw material decomposition reaction speed, to prevent the mixture from The crucible overflowed, the mixture was calcined at 1300 °C for 5 hours, cooled to room temperature (25 °C) with the furnace, and ground to obtain a new type of white light LED Mn ⁴⁺ ion-doped gallate red fluorescent material; X-ray diffraction analysis showed that the prepared The red fluorescent material is SrLaGa ₃ O ₇ crystal phase; the spectral properties of the fluorescent powder are similar to those of Example 1.

What is described in the above-mentioned embodiments and specification is only to illustrate the principle and best embodiment of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements all fall within the scope of the present invention. within the scope of the claimed invention.

Claims (10)

1. The manganese ion doped gallate red fluorescent material for the white light LED is characterized in that Mn is used for replacing Ga in crystals, the crystal structure of the material belongs to an orthorhombic system, and the chemical composition molecular formula is SrLaGa₃O₇:Mn⁴⁺The activating ion is Mn⁴⁺；

The element molar ratio is Sr, La, Ga and Mn which are 1:1:3(1-x) 3x, wherein x is more than or equal to 0 and less than 0.1.

2. The manganese ion-doped gallate red fluorescent material for the white light LED according to claim 1, wherein: and x is 0.001.

3. A preparation method of manganese ion doped gallate red fluorescent material for a white light LED is characterized by comprising the following steps:

s1), in terms of element molar ratio Sr: La: Ga: Mn ═ 1:1:3(1-x):3x, where x is 0 ≦ 0.1; respectively weighing compound raw materials containing strontium, lanthanum, gallium and manganese;

s2), grinding and uniformly mixing the compound raw materials weighed in the step S1), and then pre-sintering in an oxidizing atmosphere at the temperature of 400-600 ℃ for 2-4 hours;

s3), taking out the sample subjected to the pre-sintering in the step S2), grinding and uniformly mixing, and then firing in an oxidizing atmosphere at the temperature of 650-950 ℃ for 2-4 hours;

s4), taking out the sample burned in the step S3), grinding and uniformly mixing, and then burning in a secondary oxidizing atmosphere at the temperature of 1100-1300 ℃ for 4-8 hours to obtain the manganese-doped gallate red fluorescent material.

4. The method according to claim 3, wherein in step S1), the strontium-containing compound is selected from strontium carbonate and strontium nitrate.

5. The method according to claim 3, wherein in step S1), the lanthanum-containing compound is lanthanum oxide.

6. The method according to claim 3, wherein in step S1), the gallium-containing compound is selected from gallium oxide, gallium nitrate and gallium hydroxide.

7. The method for preparing manganese ion doped gallate red fluorescent material for white light LED according to claim 3 is characterized in that: in step S1), the manganese-containing compound raw material is any one of manganous oxide, manganese dioxide and manganese carbonate.

8. The method for preparing manganese ion doped gallate red fluorescent material for white light LED according to claim 3 is characterized in that: in step S1), x is 0.001.

9. The method for preparing manganese ion doped gallate red fluorescent material for white light LED according to claim 3 is characterized in that: in step S2), the oxidizing atmosphere is an air atmosphere or an oxygen atmosphere.

10. The method for preparing manganese ion doped gallate red fluorescent material for white light LED according to claim 3 is characterized in that: the fluorescent material emits red light under the excitation of near ultraviolet light or blue light, the light emission is within the range of 650-780nm, and the fluorescent material has two light emission centers of 691nm and 715 nm.

Images