A magnesium calcium germanium zirconate fluorescent powder and a preparation method thereof

Abstract

The application discloses a rare earth ion doped magnesium calcium germanate zirconate fluorescent powder and a preparation method thereof. 3‑x MgZrGe3O 12 :xR, wherein 0.005<=x<=0.500. Ca3MgZrGe3O 12 :xR as a matrix material, and the doped R as a central light emitting ion, and R is one or a combination of several of rare earth Ce, Tb, Eu, Dy, Sm, Bi and Cr ions. The fluorescent powder is prepared by a high-temperature solid phase method. Powder diffraction data show that the sample belongs to a garnet crystal phase. The prepared fluorescent powder can be excited by violet light or blue light, and has a strong light output in a visible light region. The magnesium calcium germanate zirconate fluorescent powder is simple to manufacture, has good light stability, and can be used for a light emitting layer of a white light LED.

Description

TECHNICAL FIELD

[0001] The present application relates to a phosphor for white LED, in particular to a germanate-zirconate-calcium-magnesium garnet phosphor and a preparation method thereof, and belongs to the technical field of inorganic luminescent materials. BACKGROUND

[0002] White light emitting diodes (W-LEDs) have gradually replaced incandescent lamps and fluorescent lamps due to their significant performance advantages such as high luminous efficiency, long service life, low power consumption and environmental protection. According to the statistics of the U.S. Department of Energy in 2012, if W-LEDs can be widely used in the next 20 years, about 20% of power consumption will be saved, so the development of W-LEDs is the trend of the times. There are three common ways to achieve W-LEDs: the first type is to use a combination of three primary color LEDs, i.e. to obtain white light by combining red, green and blue LEDs. The second type is to combine yellow luminescent phosphor Y3Al5O 12 :Ce 3+ (YAG:Ce 3+ ) with a blue InGaN chip. The third type is to use an ultraviolet / near-ultraviolet LED chip combined with three primary color phosphors. In the second scheme, YAG:Ce 3+ phosphor is low in cost and simple to encapsulate, so this combination is one of the simplest and most effective methods to produce W-LEDs. However, due to the lack of red components, the obtained white light has a low color rendering index (CRI / Ra < 80), a high correlated color temperature (CCT > 6000K) and poor high-temperature stability, which is difficult to meet the demand of high-quality lighting. Therefore, the development of new phosphors is of great significance to promote the development and application of LEDs.

[0003] At present, the garnet structure matrix generally has good physical and chemical stability, high light transmittance in the visible light region, and can form various solid solutions by ion replacement, and is widely used as a matrix material for phosphors. The garnet structure belongs to the cubic system (Ia3d) space group, and the general formula is A3B2C3O 12 which can also be written as A3B2(CO4)3, wherein A, B and C represent cations occupying 24c, 16a and 24d positions, respectively, and are combined with 8, 6 and 4 oxygen atoms to form dodecahedron, octahedron and tetrahedron. It can be seen that there are three different cation sites in the garnet structure, and new garnet structure phosphors can be further synthesized by substitution of different cations or cation units. For YAG:Ce 3+ , first, the A-site cation can be substituted, for example, lanthanide ions (Lu 3+ , Gd 3+ , Tb3+ ) and alkaline earth metal ions (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) to regulate, wherein the substitution of lanthanide ions is generally a single A-site substitution, such as LuAG:Ce 3+ , GdAG:Ce 3+ , TbAG:Ce 3+ . While the substitution of alkaline earth metal ions at the A-site, due to the difference in valence from the valence of Y 3+ at the A-site, in order to consider the problem of charge balance of the system, the substitution is a chemical unit co-substitution, which is usually Mg 2+ -Si 4+ / Ge 4+ , Ca 2+ -Si 4+ / Ge 4+ , such as Lu2Mg2Al2Si2O 12 :Ce 3+ , CaY2Al4SiO 12 :Ce 3+ . Secondly, when substituting at the B-site, it is also through the selection of ions with similar ionic radii such as Ga 3+ , Sc 3+ , Sb 3+ , Mg 2+ and Mn 2+ , and similarly when substituting at the C-site, it is also through the selection of ions with similar ionic radii such as Ga 3+ , Ge 4+ and Si 4+ . As shown above, when substituting with ions of different valences, chemical unit substitution is usually used, and due to the difference in ionic radius of the substituted ions, it will usually cause the emission of the luminescent ions after substitution to have different degrees of red shift or blue shift. For example, Y2Mg2Al2Si2O 12 :Ce 3+ ; wherein Mg 2+ -Si 4+ is doped at the B and C sites, respectively, resulting in a red shift of Ce 3+ emission, but the substitution of Mg 2+ -Si 4+ at the A and C sites makes the Ce 3+ emission blue shift.

[0004] Overall, the development of germanate series fluorescent powder is relatively late, and the main protection of the germanate matrix with rare earth elements Y, Gd, Lu and other elements is still in its infancy, the types are few, the luminescent efficiency is low, and there are still many contents to be studied. SUMMARY

[0005] To address the problems of difficult luminescent material preparation, poor spectral matching, and low luminous efficiency in existing technologies, this invention provides a garnet-type magnesium calcium germanate zirconate phosphor with low preparation temperature, simple process, and environmental friendliness, as well as its preparation method. This phosphor uses magnesium and calcium ions as cationic groups, which can provide vacancies for the luminescent center ion; germanate and zirconate ions as anionic groups, providing a coordination environment for the luminescent ion; and rare earth ions and heavy metal ions as luminescent ions, providing a variety of emission spectra. This phosphor can be effectively excited by violet or blue light and has light output in the visible light region, making it suitable for use as the luminescent layer in semiconductor lighting devices.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned phosphor.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention relates to magnesium calcium germanate phosphor, with the general chemical formula Ca. 3-x MgZrGe3O 12 :xR, where 0.005≤x≤0.500; Ca3MgZrGe3O 12 As a matrix material, the doped R serves as the central luminescent ion, and R is one or a combination of rare earth ions such as Ce, Tb, Eu, Dy, Sm, Bi, and Cr.

[0009] This invention exhibits excellent fluorescence performance in the visible light band, with an effective excitation wavelength between 300 and 500 nm and an emission wavelength between 400 and 700 nm.

[0010] The above-mentioned magnesium calcium germanate phosphor is prepared by a high-temperature solid-state method, including the following steps:

[0011] (1) According to Ca 3-x MgZrGe3O 12 The stoichiometric ratio of xR is as follows: CaCO3, MgO, ZrO2, and SiO2 with a purity higher than 99% are weighed as raw materials for the matrix; rare earth oxides (CeO2, Tb2O3, Eu2O3, Dy2O3, Sm2O3, Bi2O3, Cr2O3) with a purity higher than 99.99% are weighed as raw materials for luminescent ions; Li2CO3 with a purity higher than 99% is weighed as raw material for valence equilibrium Li ions; and 1% to 3% of the total weight of LiF, MgF2, or CaF2 are weighed as flux. The weighed materials are ground and mixed evenly to obtain a mixture.

[0012] (2) Place the mixture into a corundum boat, place it into a high-temperature resistance furnace, and calcine it under air or a mixture of hydrogen and nitrogen. The temperature is raised to 1100-1400℃ for calcine for 2-6 hours, and then cooled to room temperature.

[0013] (3) The cooled powder is further ground, washed and dried to obtain the magnesium calcium germanate zirconate fluorescent powder of the present application.

[0014] The types and contents of the raw materials in the present application are adjusted by those skilled in the art according to the actual needs of the present application.

[0015] The raw material of the luminescent ion is one or a combination of several of CeO2, Tb2O3, Eu2O3, Dy2O3, Sm2O3, Bi2O3 and Cr2O3.

[0016] The fluxing agent is one or a combination of several of LiF, MgF2 and CaF2.

[0017] The rate of temperature programming is 50-300℃ / hour, and the drying temperature is 80-200℃.

[0018] The roasting atmosphere is air or a mixture of hydrogen and nitrogen. The mixture of hydrogen and nitrogen is a mixture of 5% hydrogen and 95% nitrogen by volume.

[0019] The present application has the following advantages:

[0020] (1) The germanate and zirconate ions are compounded to prepare the magnesium calcium germanate zirconate fluorescent powder;

[0021] (2) The substrate material does not contain rare earth ions, thereby reducing the amount of rare earth ions;

[0022] (3) The fluorine compound fluxing agent is used for roasting at a lower temperature, thereby reducing the preparation cost and improving the product purity;

[0023] (4) The emission spectrum is adjusted by replacing the luminescent ion;

[0024] (5) The product has good thermal stability and chemical stability;

[0025] (6) The product can be effectively excited by violet light and blue light;

[0026] (7) The Li ion is used to balance the valence state and optimize the luminescent properties;

[0027] (8) The product has potential application prospects in the field of white light LED lighting. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the X-ray diffraction pattern of Ca 3-x MgZrGe3O 12 : x Dy 3+ .

[0029] Figure 2 is the excitation spectrum of Ca 3-x MgZrGe3O 12 : x Dy 3+ ;

[0030] Figure 3 is the emission spectrum of Ca 3-x MgZrGe3O 12 : x Dy 3+ ;

[0031] Figure 4 is the excitation spectrum of Ca 3-x MgZrGe3O 12 : x Tb 3+ ;

[0032] Figure 5 is the emission spectrum of Ca 3-x MgZrGe3O 12 : x Tb 3+ ;

[0033] Figure 6 is the luminescence color of Ca 3-x MgZrGe3O 12 : x Eu 3+ under UV light.DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. All the raw materials in the present application are commercially available products.

[0035] Embodiment 1:

[0036] Ca 3-x MgZrGe3O 12 : x Dy 3+ fluorescent powder.

[0037] According to the stoichiometric ratio, 2.60-3.00 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.037-0.370 grams of dysprosium sesquioxide, 0.01-0.07 grams of lithium carbonate, 0.08 grams of lithium fluoride are weighed, and the weighed raw materials are placed in an agate mortar, and the powder is ground and mixed uniformly.

[0038] Then the mixed raw materials are placed in a corundum boat, heated to 1250℃ at a heating rate of 100℃ / hour in an air atmosphere in a high-temperature resistance furnace, and kept at this temperature for 3 hours, and then slowly cooled to room temperature.

[0039] The sintered sample is ground into powder, washed with deionized water and ethanol for three times respectively to remove residual impurities, and dried at 200℃ for 2 hours to obtain a luminescent powder with uniform particle size.

[0040] The prepared Ca 3-x MgZrGe3O 12 : x Dy 3+ The inventor tested the structure and performance of the fluorescent powder, and the X-ray diffraction pattern is shown in Figure 1 , the excitation spectrum is shown in Figure 2 , and the emission spectrum is shown in Figure 3 . Figure 1 The diffraction peaks of the synthesized fluorescent powder are consistent with those of the garnet Ca3Ge3Sc2O 12 , indicating that the crystal phase of the fluorescent powder is garnet type, the excitation spectrum shows that the fluorescent powder can be excited by violet or blue light, and the emission spectrum shows that the fluorescent powder can emit red light.

[0041] Example 2:

[0042] Ca 3-x MgZrGe3O 12 : x Tb 3+ Synthesis of fluorescent powder

[0043] According to the stoichiometric ratio, 2.28-3.00 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.037-0.659 grams of dysprosium sesquioxide, 0.01-0.14 grams of lithium carbonate, 0.08 grams of magnesium fluoride and 0.08 grams of lithium fluoride are weighed, and the weighed raw materials are placed in an agate mortar, and the powder is ground and mixed uniformly.

[0044] Then the mixed raw materials are placed in a corundum boat, heated to 1250℃ at a heating rate of 100℃ / hour in an air atmosphere in a high-temperature resistance furnace, and kept at this temperature for 3 hours, and then slowly cooled to room temperature.

[0045] The sintered sample was ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and dried at 150°C for 6 hours to obtain the luminescent powder with uniform particle size. 3-x MgZrGe3O 12 : x Tb 3+ The excitation spectrum of the sample is shown in Fig. 2, indicating that the sample can be effectively excited by ultraviolet light. Figure 4 Ca 3-x MgZrGe3O 12 : x Tb 3+ The emission spectrum of the sample is shown in Fig. 3, indicating that the sample emits bright green light under ultraviolet excitation. Figure 5

[0046] Example 3:

[0047] Ca 3-x MgZrGe3O 12 : x Eu 3+ Synthesis of the fluorescent powder

[0048] According to the stoichiometric ratio, 2.20-3.0 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.037-0.43 grams of europium sesquioxide, 0.01-0.16 grams of lithium carbonate, and 0.05 grams of magnesium fluoride were weighed. The weighed raw materials were placed in an agate mortar, and the powder was ground and mixed uniformly by grinding.

[0049] Subsequently, the mixed raw materials were placed in a corundum boat and heated to 1400°C at a heating rate of 50°C / hour in an air atmosphere in a high-temperature resistance furnace, and maintained at this temperature for 6 hours, and then slowly cooled to room temperature.

[0050] The sintered sample was ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and dried at 150°C for 6 hours to obtain the luminescent powder with uniform particle size. 3-x MgZrGe3O 12 : x Eu 3+ The luminescent color under ultraviolet lamp is shown in Fig. 4, Figure 6 Figure 6 The surface sample can convert ultraviolet light into bright red light.

[0051] Example 4:

[0052] Ca 3-x MgZrGe3O 12 : x Eu 2+ Synthesis of the fluorescent powder.​​

[0053] 2.60-3.0 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.037-0.370 grams of europium sesquioxide, 0.01-0.04 grams of lithium carbonate, and 0.08 grams of calcium fluoride are weighed according to the stoichiometric ratio, and the weighed raw materials are placed in an agate mortar, and the powders are ground and mixed uniformly by grinding.

[0054] The mixed raw materials are then placed in a corundum boat, heated to 1300°C at a heating rate of 300°C / hour in a high-temperature resistance furnace under the protection of a mixed gas of nitrogen and hydrogen, and kept at this temperature for 2 hours, and then slowly cooled to room temperature.

[0055] The sintered sample is ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and baked at 80°C for 20 hours to obtain a luminescent powder with uniform particle size.

[0056] Example 5:

[0057] Ca 3-x MgZrGe3O 12 : x Bi 3+ Synthesis of fluorescent powder.

[0058] 2.80-3.0 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.012-0.466 grams of bismuth sesquioxide, 0.01-0.07 grams of lithium carbonate, and 0.04 grams of calcium fluoride are weighed according to the stoichiometric ratio, and the weighed raw materials are placed in an agate mortar, and the powders are ground and mixed uniformly by grinding.

[0059] The mixed raw materials are then placed in a corundum boat, heated to 1200°C at a heating rate of 100°C / hour in a high-temperature resistance furnace under an air atmosphere, and kept at this temperature for 4 hours, and then slowly cooled to room temperature.

[0060] The sintered sample is ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and baked at 120°C for 10 hours to obtain a luminescent powder with uniform particle size.

[0061] Example 6:

[0062] Ca 3-x MgZrGe3O 12 : x Cr 3+ Synthesis of fluorescent powder.

[0063] Take 2.80-3.0 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.015-0.150 grams of chromium trioxide, 0.01-0.07 grams of lithium carbonate, 0.04 grams of calcium fluoride according to the stoichiometric ratio, put the weighed raw materials in the agate mortar, grind the powder finely and mix uniformly by grinding.

[0064] Subsequently, the mixed raw materials are placed in a corundum boat, heated to 1200°C at a heating rate of 100°C / hour in a high-temperature resistance furnace under air atmosphere, and kept at this temperature for 4 hours, and then slowly cooled to room temperature.

[0065] The sintered sample is ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and baked at 200°C for 2 hours to obtain a luminescent powder with uniform particle size.

[0066] Example 7:

[0067] Ca 2.98 MgZrGe3O 12 :0.02Eu 3+ ,0.02Tb 3+ Synthesis of fluorescent powder.

[0068] Take 2.92 grams of calcium carbonate, 0.40 grams of magnesium oxide, 1.23 grams of zirconium oxide, 3.14 grams of germanium oxide, 0.035 grams of europium trioxide, 0.037 grams of terbium trioxide, 0.02 grams of lithium carbonate, and 0.04 grams of calcium fluoride according to the stoichiometric ratio, put the weighed raw materials in the agate mortar, grind the powder finely and mix uniformly by grinding.

[0069] Subsequently, the mixed raw materials are placed in a corundum boat, heated to 1280°C at a heating rate of 100°C / hour in a high-temperature resistance furnace under air atmosphere, and kept at this temperature for 6 hours, and then slowly cooled to room temperature.

[0070] The sintered sample is ground into powder, washed with deionized water and ethanol for three times respectively to remove the residual impurities, and baked at 100°C for 6 hours to obtain a luminescent powder with uniform particle size.

[0071] The fluorescent powder prepared in Examples 2-7 has an effective excitation wavelength of 300-500 nm and an emission wavelength of 400-700 nm, has high thermal stability and chemical stability, and has potential application prospects in the field of white light LED lighting.

Claims

1. A magnesium calcium germanate phosphor with the general chemical formula Ca 3-x MgZrGe3O 12 :xR, where 0.04≤x≤0.44; Ca3MgZrGe3O 12 As the matrix material, the doped R serves as the central luminescent ion, and R is one or a combination of rare earth Ce, Tb, Eu, Dy, Sm, and Bi ions; Li ions are used to balance the valence state.

2. The preparation method of magnesium calcium germanate phosphor as described in claim 1, characterized in that: (1) According to Ca 3-x MgZrGe3O 12 The stoichiometric ratio of CaCO3, MgO, ZrO2 and GeO2 as matrix raw materials, rare earth R oxides, Li2CO3 and fluorides as luminescent ion raw materials are weighed out. All materials are ground and mixed evenly to obtain a mixture; the fluoride is selected from LiF, MgF2 or CaF2. (2) Place the mixture into a corundum boat, place it into a high-temperature resistance furnace, and calcine it in an atmosphere of air or a mixture of hydrogen and nitrogen. The temperature is raised to 1100-1400℃ for calcine for 2-6 hours, and then it is naturally cooled to room temperature. (3) Grind the cooled powder, then wash and dry it with deionized water and ethanol to obtain magnesium calcium germanate phosphor.

3. The preparation method of magnesium calcium germanate phosphor as described in claim 2, characterized in that: The purity of CaCO3, Li2CO3, MgO, ZrO2, and GeO2 is higher than 99%; the purity of rare earth R oxides, the raw materials for luminescent ions, is higher than 99.99%.

4. The preparation method of magnesium calcium germanate phosphor as described in claim 2, characterized in that: Rare earth R oxides are one or a combination of CeO2, Tb2O3, Eu2O3, Dy2O3, Sm2O3, and Bi2O3.

5. The method for preparing magnesium calcium germanate phosphor according to any one of claims 2-4, characterized in that: Fluorides account for 1% to 3% of the total material weight.

6. The method for preparing magnesium calcium germanate phosphor according to any one of claims 2-4, characterized in that: In step (2), the mixture of hydrogen and nitrogen is a mixture of 5% hydrogen and 95% nitrogen, by volume percentage.

7. The method for preparing magnesium calcium germanate phosphor according to any one of claims 2-4, characterized in that: The R oxide is europium trioxide, terbium trioxide, or dysprosium trioxide.

8. The method for preparing magnesium calcium germanate phosphor according to any one of claims 2-4, characterized in that: The programmed heating rate is 50–300 °C / hour.

9. The method for preparing magnesium calcium germanate phosphor according to any one of claims 2-4, characterized in that: The drying temperature is 80~200℃.

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