CN102936497B - Main emission peak changeable and adjustable fluorescent material and preparation method thereof - Google Patents

Abstract

A fluorescent material with adjustable emission main peak and a preparation method thereof. The invention relates to a fluorescent material for LED lighting/display and a preparation method thereof, which is an alkaline earth oxyfluorosilicate fluorescent material, and the general chemical formula is: M _xz Y _6-xyz Al _11-x L _x O _{25.5-0.5 k} F _k : yCe ³⁺ , zMn ²⁺ , where Ce ³⁺ and Mn ²⁺ are luminescent center ions, in the general formula: 0≤x≤1.5, 0.01≤y≤0.16, 0≤z≤0.2, 0<k ≤0.01; M is Mg ²⁺ or Ba ²⁺ , L is Si ⁴⁺ or Zr ⁴⁺ ; according to the general chemical formula, MgO, MgF ₂ , Al ₂ O ₃ , AlF ₃ , SiO ₂ , ZrO ₂ , BaF ₂ , BaCO ₃ , MnCO ₃ and CeO ₂ , mixed in a closed container, kept the mixture in a reduction furnace at 1620°C under H ₂ atmosphere, cooled, crushed and classified, and sieved to obtain alkaline earth fluorooxyaluminosilicate fluorescent materials . The invention provides a fluorescent material with a wavelength of 530-585nm, a fluorescent material with a wavelength of 530-585nm, which can be adjusted for white light LED lighting/display, and whose main emission peaks are adjustable in green, yellow, and orange.

Description

A fluorescent material with adjustable emission main peak and its preparation method

technical field

The invention relates to a fluorescent material and a preparation method thereof, in particular to a fluorescent material and a preparation method thereof in application fields such as LED lighting/display.

Background technique

White LED is a new solid-state green lighting technology with high efficiency, energy saving and environmental protection, and is known as the fourth generation lighting source in the 21st century. The realization _scheme of white light LED mainly includes: 1) using red _, green and blue three primary color chips to prepare high color rendering white light LED _; Ce ³⁺ ) yellow phosphor; 3) using UV-LED to excite red, green and blue phosphors to prepare white LED with high color rendering. Judging from the current development trend of white light LED lighting technology, the realization of white light LED is mainly based on fluorescence conversion, that is, through blue LED (450~470nm) to excite yellow phosphor YAG:Ce, (Ba,Sr)SiO ₄ :Eu ²⁺ , that is, blue LED + yellow phosphor; or ultraviolet LED (380 ~ 400nm)) to excite blue, green and red phosphor, that is, the combination of purple LED + RGB phosphor to obtain a white LED. Therefore, the performance of fluorescent materials plays a vital role in the light efficiency, light decay and color rendering of white LEDs.

CN201110309206.9 discloses a method for preparing yttrium aluminum garnet structure YAG:Ce rare earth phosphor by a high-temperature solid phase method, and weighs Y ₂ O ₃ or Gd ₂ O according to the molar ratio of Y ₃ Al ₅ O ₁₂ :Ce phosphor chemical formula ₃ or their mixtures, Al ₂ O ₃ or Ga ₂ O ₃ or their mixtures, CeO ₂ and flux, and bake in a reducing atmosphere of a high-temperature furnace for 2 to 6 hours to obtain YAG:Ce rare earth phosphors.

CN201110132661.6 discloses a LED phosphor, which is a garnet phase material with cerium, chromium ions or Ce+Cr co-doped as the active center, at least one element selected from Y and rare earth, at least one Selected from Al, Ga, In, Sc, V, the introduction of element vanadium in the matrix is conducive to the improvement of fluorescence efficiency, the introduction of vanadium helps to improve the lattice integrity of matrix doping, and at the same time, vanadium doping can affect the matrix The luminescent center in the luminescence plays a role of fluorescence sensitization, and the introduction of chromium can bring more abundant red fluorescent components above 600nm, and improve the display of the phosphor.

CN201110186964.6 discloses a silicate yellow-orange fluorescent powder, which is composed of materials represented by the general formula Sr _2-xyz Lu _y B _z SiO ₄ :xEu ²⁺ , where x is the number of moles of europium atoms, and y is lutetium The number of moles of atoms, z is the number of moles of barium atoms, 0.005≤x≤0.15, 0.01≤y≤0.15, 0≤z≤1.5. Under the excitation of 460nm blue light, its emission spectrum is a band line at 470-700nm, and the central wavelength moves between 515-570nm with the increase of barium doping amount.

The above-mentioned CN201110309206.9 and CN201110132661.6 phosphor powders for LEDs belong to the aluminate YAG:Ce system; CN201110186964.6 belongs to silicate (Sr, Ba) ₂ SiO ₄ :Eu ²⁺ phosphor powders, and the phosphor powders of CN201110132661.6 Chromium, a toxic element, is added as a luminescent ion.

At present, the color temperature of incandescent lamps and fluorescent lamps used by people is generally lower than 6000K, because low color temperature light has many advantages such as strong ability to penetrate fog and water vapor, soft light, and high reflectivity of the road surface. However, commercial YAG:Ce phosphors In the emission spectrum, the main emission peak can only reach 560nm, and the red light component is less, resulting in a high color temperature (6000-8000K) and a low color rendering index (<80) of the white LED device. Therefore, it is necessary to improve the color rendering of white LEDs by adding orange and red phosphors. Although the silicate phosphor (Sr, Ba) ₂ SiO ₄ :Eu ²⁺ has the characteristics of adjustable emission main peak 515-570nm, the silicate material system phosphor has the disadvantages of large light attenuation and low thermal stability. , especially the red light part can only reach about 570nm, which is far from meeting the requirements of improving the color rendering of white light LEDs.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a white light LED lighting/display with green, yellow and orange emission main peaks that can be adjusted, has higher luminous efficiency under the excitation of blue light LEDs, and has a fluorescent light with a wavelength of 530-585nm. Materials and their preparation methods.

The present invention should be widely used as alkaline earth oxyfluorosilicate fluorescent material, and its general chemical formula is expressed as: M _xz Y _6-xyz Al _11-x L _x O _25.5-0.5k F _k : yCe ³⁺ , zMn ²⁺ , where Ce ³⁺ and Mn ²⁺ are luminescent central ions, in the general formula: 0≤x≤1.5, 0.01≤y≤0.16, 0≤z≤0.2, 0<k≤0.01; M is Mg ²⁺ or Ba ^{2 +} , L is Si ⁴⁺ or Zr ⁴⁺ ; according to the general chemical formula, analytically pure MgO, MgF ₂ , NH ₄ F, Al ₂ O ₃ , AlF ₃ , SiO 2 , ZrO ₂ , BaF _{2 ,} BaCO ₃ , MnCO ₃ and CeO ₂ were mixed according to the chemical composition ratio, and mixed in a closed container for 40 hours, and then the mixture was kept in a reduction furnace at 1620°C for 6 hours under the atmosphere of H ₂ %<5%, cooled, crushed and classified, and passed 500-mesh sieve to obtain the alkaline earth oxyfluorosilicate fluorescent material with a particle size of about 3-20 μm.

The crystal structure of the alkaline earth oxysilicoaluminate zirconate fluorescent material is shown in Figure 1. There is one Y ³⁺ site and two Al ³⁺ sites in the material system. Because the ionic radii of Al ³⁺ , Si ⁴⁺ , and Zr ⁴⁺ are 0.061, 0.040, and 0.065 nm, respectively, while the ionic radii of Y ³⁺ , Mg ²⁺ , Ba ²⁺ , Mn ²⁺ , and Ce ³⁺ are 0.089, 0.072 nm, respectively. , 0.135, 0.08 and 0.13nm. According to the principle of similar ionic radii, Si ⁴⁺ and Zr ⁴⁺ preferentially replace the AlO ₄ and AlO ₆ sites in the crystal structure of the alkaline earth oxyfluorosilicoaluminate fluorescent material, while Mg ²⁺ , Ba ²⁺ , and Mn ²⁺ And Ce ³⁺ plasma replaces the YO ₈ site in the crystal structure of the alkaline earth oxysilica zirconium aluminate fluorescent material.

The crystal field level splitting of Ce ³⁺ has great influence on the surrounding coordination environment. Si ⁴⁺ has an electronegativity of 1.9, while Al ³⁺ has an electronegativity of 1.6. When a Si ⁴⁺ ion with a higher electronegativity replaces the Al ³⁺ with a lower electronegativity, the covalency of the coordination field around Ce ³⁺ is enhanced, resulting in greater energy level splitting of Ce ³⁺ , the center of gravity of the lowest 5d orbital energy level d ₁ level drops obviously, which makes the emission of Ce ³⁺ appear red shifted. The same principle, when Zr ⁴⁺ replaces Al ³⁺ , because the electronegativity of Zr ⁴⁺ is 1.33, the covalency of the coordination field around Ce ³⁺ is reduced, thereby reducing the crystal field energy level split of Ce ³⁺ The center of gravity of the lowest 5d orbital energy level d ₁ level rises obviously, which makes the emission of Ce ³⁺ appear blue-shifted.

Therefore, according to the above mechanism, adjusting the content of Zr ⁴⁺ and Si ⁴⁺ in the matrix components can adjust the crystal field splitting level of the Ce ³⁺ site, so that the emission of Ce ³⁺ ions from green (530nm) Adjustable to yellow (570nm).

When Zr ⁴⁺ and Si ⁴⁺ replace Al ³⁺ ions, unequal substitutions will occur, and defects are easily formed, thereby forming luminescent quenching centers, which is very unfavorable for improving the luminous efficiency of rare earth fluorescent materials. Therefore, alkaline earth ions such as Mg ²⁺ and Ba ²⁺ are introduced into the fluorescent material system of the present invention, and Mg ²⁺ and Ba ²⁺ are unequivalently substituted for the sites of Y ³⁺ , so that the crystal structure of the fluorescent material maintains charge balance.

However, although the emission of Ce ³⁺ ions in the phosphor can be red-shifted from 545nm to about 570nm by doping Si ⁴⁺ , in order to improve the color rendering index of low color temperature white LEDs, it is necessary to further red-shift the emission of Ce ³⁺ . Because the lowest 5d orbital energy level of Ce ³⁺ is located at 460nm of blue light, it has higher luminous efficiency under blue light excitation. However, although Mn ²⁺ absorbs some at 430nm, the luminescence is relatively weak. Therefore, in the present invention, we design a Ce ³⁺ and Mn ²⁺ co-doped fluorescent material system, and use the Ce ³⁺ →Mn ²⁺ energy transfer principle (ET) to obtain an orange fluorescent material. First, the blue light is absorbed through the Ce ³⁺ ion d ₁ orbital energy level, and then the energy is non-radiatively transferred to the Mn ²⁺ ion ⁴ T ₁ (G) matching energy level, and finally through ^{the 4} T ₁ (G) of Mn ²⁺ → ⁶ A ₁ energy level transition to achieve orange light broadband emission, the main emission peak is located at 585nm.

The alkaline earth oxyfluoride silicon zirconium aluminate fluorescent material of the present invention has higher luminous efficiency under blue light excitation, and at the same time makes up for the shortcomings of YAG:Ce fluorescent powder such as lack of red light parts.

Fig. 2, 3 has respectively provided the XRD and the emission spectrogram of the fluorescent material prepared by embodiment 1, 2, 3, 4, as seen from Fig. 2, 3, adding a small amount of silicon does not affect this material crystal structure, along with the fluorescent material As the content of Si increases, the emission spectrum gradually shifts from 545nm to 570nm. Fig. 4 shows the scanning electron microscope (SEM) photo of the fluorescent material prepared in Example 1. The fluorescent material is a spherical particle with a particle size of 3-10 μm. Figures 5 and 6 show the emission spectrum and chromaticity coordinates of the packaged white LED. Under the excitation of 350mA current, the white LED has a color temperature Tc=5823K, color coordinates X=0.3241, Y=0.3676, and a luminous efficacy of 121.5 lumens/ Watts, color rendering index 78.5.

Figures 7 and 8 show the excitation and emission spectra of the fluorescent materials prepared in Examples 5, 6 and 7. As the Ce concentration increases, the excitation and emission spectra gradually red shift. Figures 9 and 10 show the emission spectrum and chromaticity coordinates of the packaged white LED. Under the excitation of 350mA current, the white LED has a color temperature Tc=5430K, color coordinates X=0.3352, Y=0.4072, and a luminous efficacy of 113.2 lumens/ watts, color rendering index 79.2.

Figures 11, 12, 13 and 14 show the XRD crystal structure diffraction, excitation and emission spectra and X-ray fluorescence spectrum (XPS) of the fluorescent material prepared in Example 8. By doping Zr ⁴⁺ elements, the crystal structure is basically unchanged, but from the X-ray photoelectron spectroscopy (XPS) of the fluorescent material in Figure 14, it is found that in addition to Y, Al, O, and Ce, the material structure contains Zr ^{4 +} and Mg ²⁺ and other elements, indicating that in the fluorescent material of the present invention, Zr ⁴⁺ and Mg ²⁺ ions have entered the crystal lattice. From the Ce ³⁺ excitation spectrum, it is found that the 360nm excitation band is obviously reduced, and the lowest 5d orbital energy level of Ce ³⁺ is obviously blue-shifted. It is also found in the emission spectrum that the emission spectrum gradually shifts blue by about 545nm, thereby achieving a blue shift of the emission spectrum to obtain a greener fluorescent material. Figures 15 and 16 show the emission spectrum and chromaticity coordinates of the packaged white LED. Under the excitation of 350mA current, the white LED has a color temperature Tc=5658K, color coordinates X=0.3282, Y=0.3818, and a luminous efficacy of 106.9 lumens/ watts, color rendering index 79.2.

Figures 17, 18, 19 and 20 show the XRD crystal structure diffraction, excitation and emission spectra and X-ray fluorescence spectrum (XPS) of the fluorescent material prepared in Example 11. By doping Si ⁴⁺ and Mn ²⁺ elements, the crystal structure is basically unchanged, but from the X-ray photoelectron spectrum (XPS) of the fluorescent material in Figure 20, it is found that in addition to Y, Al, O, and Ce in the material structure, Elements such as Si ⁴⁺ and Mn ²⁺ are contained, indicating that in the fluorescent material of the present invention, Si ⁴⁺ and Mg ²⁺ ions enter the crystal lattice. From the Ce ³⁺ excitation spectrum, it is found that there are three excitation bands in total, the excitation bands at 297, 334 and 462nm are significantly reduced, and the excitation band at 297nm comes from the Mn ²⁺ excitation band, as shown in Figure 18. Figure 19 shows the emission spectrum of Ce ³⁺ and Mn ²⁺ ion co-doped fluorescent materials. Through Gaussian fitting and peak division, it is found that the emission band is mainly composed of three emission bands at 530, 585 and 733nm, and the 530nm emission band comes from The 5d → ² F _5/2 energy level transition of Ce ³⁺ , and the 585nm and 733nm are from ^{the 4} T ₁ → ¹ A ₆ energy level transition of Mn ²⁺ . Figure 21 and Figure 22 show the emission spectrum and chromaticity coordinate diagram of the packaged white LED. Under the excitation of 350mA current, the white LED has a color temperature Tc=3947K, color coordinates X=0.4109, Y=0.4778, and a luminous efficacy of 98.5 lumens / watt, color rendering index 86.6.

Description of drawings

Fig. 1 schematic diagram of crystal structure of fluorescent material of the present invention;

The crystal structure X-ray diffractogram (XRD) of Fig. 2 embodiment 1,2,3,4 fluorescent material;

Fig. 3 embodiment 1,2,3,4 fluorescent material emission spectrum;

The fluorescent powder scanning electron microscope picture (SEM) that Fig. 4 embodiment 1 obtains;

The spectrum diagram of white light LED obtained by packaging in Fig. 5;

The chromaticity diagram of the white light LED obtained by packaging in Fig. 6;

Fig. 7 embodiment 5,6,7 fluorescent material excitation spectrogram;

Fig. 8 embodiment 5,6,7 fluorescent material emission spectrogram;

The spectrum diagram of the white light LED obtained by packaging in Fig. 9;

The chromaticity diagram of white light LED obtained by packaging in Fig. 10;

The crystal structure X-ray diffractogram (XRD) of the fluorescent material prepared in Fig. 11 embodiment 8;

The excitation spectrum of the fluorescent material prepared in Fig. 12 Example 8;

The emission spectrum diagram of the fluorescent material prepared in Fig. 13 embodiment 8;

The fluorescent material X-ray photoelectron spectrum (XPS) that Fig. 14 embodiment 8 prepares;

Figure 15 is a white light LED spectral diagram obtained by packaging;

The chromaticity diagram of the white LED obtained by packaging in Fig. 16;

The crystal structure X-ray diffractogram (XRD) of the fluorescent material prepared in Fig. 17 embodiment 11;

The excitation spectrum of the fluorescent material prepared in Fig. 18 embodiment 11;

The emission spectrum diagram of the fluorescent material prepared in Fig. 19 embodiment 11;

The fluorescent material X-ray photoelectron spectrum (XPS) that Fig. 20 embodiment 11 prepares;

Fig. 21 is a white light LED spectral diagram obtained by packaging;

Fig. 22 The chromaticity diagram of the packaged white LED.

Detailed ways

According to the general chemical formula M _xz Y _6-xyz Al _11-x L _x O _25.5-0.5k F _k : y.Ce ³⁺ , z.Mn ²⁺ , analytically pure MgO, MgF ₂ , NH ₄ F, Al ₂ O ₃ , AlF ₃ , SiO ₂ , ZrO ₂ , BaF ₂ , MnCO ₃ and CeO ₂ were mixed according to the chemical composition ratio of Table 1, 2 and 3, mixed in a closed container for 40 hours, and then the mixture was heated in H ₂ %<5% atmosphere, keep warm in a reduction furnace at 1620°C for 6 hours, cool, crush and classify, and pass through a 500-mesh sieve to obtain an alkaline earth fluorooxyaluminosilicate fluorescent material with a particle size of about 3-20 μm. Combine and package with blue LED chip (450-460nm) to obtain white LED.

The main peak of phosphor emission is determined by the national phosphor test standard GB/T 14634.2-2010, and the excitation spectrum is tested by FLS-920 transient steady-state fluorescence spectrometer. The crystal structure (XRD) of the phosphor is determined by the GB/T 19421.1-2003 test standard. The color temperature (CCT), color rendering index (Ra), emission spectrum, and luminous efficiency (lm/w) of white LEDs are determined by the GB/T 24982-2010 test method. The phosphor photoelectron spectroscopy (XPS) is determined by the ISO15472-2001 test method.

Table 1 Chemical Composition of Fluorescent Materials

Table 2 Chemical Composition of Fluorescent Materials

Table 3 Chemical Composition of Fluorescent Materials

Claims (2)

1. launch main peak and change an adjustable fluorescent material, it is characterized in that chemical general formula is expressed as: M for alkaline earth fluorine oxygen silico-aluminate fluorescent material _x-zy _6-x-y-zal _11-xl _xo _25.5-0.5kf _k: yCe ³⁺, zMn ²⁺, wherein Ce ³⁺and Mn ²⁺for luminescent center ion, in general formula: 0 < x≤1.5,0.01≤y≤0.16,0≤z≤0.2,0 < k≤0.01; M is Mg ²⁺or Ba ²⁺, L is Si ⁴⁺or Zr ⁴⁺; According to chemical general formula, by analytically pure MgO, MgF ₂, NH ₄f, Al ₂o ₃, AlF ₃, SiO ₂, ZrO ₂, BaF ₂, BaCO ₃, MnCO ₃and CeO ₂, in chemical constitution ratio batching mixing, batch mixing 40 hours in encloses container, then by mixture at H ₂under % < 5% atmosphere, in 1620 DEG C of reduction furnaces, be incubated 6 hours, cooling, broken classification, cross 500 eye mesh screens, obtain the alkaline earth fluorine oxygen silico-aluminate fluorescent material that granularity is 3 ~ 20 μm.

2. transmitting main peak according to claim 1 changes the preparation method of adjustable fluorescent material, it is characterized in that according to chemical general formula, by analytically pure MgO, MgF ₂, NH ₄f, Al ₂o ₃, AlF ₃, SiO ₂, ZrO ₂, BaF ₂, BaCO ₃, MnCO ₃and CeO ₂, in chemical constitution ratio batching mixing, batch mixing 40 hours in encloses container, then by mixture at H ₂under % < 5% atmosphere, in 1620 DEG C of reduction furnaces, be incubated 6 hours, cooling, broken classification, cross 500 eye mesh screens, obtain the alkaline earth fluorine oxygen silico-aluminate fluorescent material that granularity is 3 ~ 20 μm.