A sulfur oxide phosphor material, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a sulfur oxide phosphor material with a chemical formula of Ba 1‑1.5x ZnOS:xBi 3+ ; wherein, x ranges from 0.005 to 0.025; its preparation includes the following steps: 1) accurately weigh the required raw materials BaCO3, ZnS, and Bi2O3 according to the stoichiometric ratio of Ba 1‑1.5x ZnOS:xBi 3+ ; 2) grind and dry the weighed raw materials; 3) calcine under a protective atmosphere, cool to room temperature, and grind to obtain the sulfur oxide phosphor. The phosphor material obtained by the present invention has strong thermal stability and fluorescence stability; and the involved preparation method is simple, non-toxic and pollution-free, and the obtained product has a high purity; when used as a fluorescence conversion material and applied in the LED field, it can exhibit excellent luminescence performance, with high light conversion efficiency and luminescence intensity.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and particularly relates to a sulfur oxide phosphor material, a preparation method thereof, and an application thereof. Background Art

[0002] Phosphors are very important light conversion materials, and by improving the luminescent properties of phosphors, they can be better applied in the field of luminescence. Solid-state lighting is the most common lighting method at present, and the exploration of lighting devices has always been a research topic for many scientific researchers. With the continuous progress of research, the most common lighting device, the light-emitting diode (LED), needs to keep advancing with the requirements of life and the development of scientific research. Compared with other lighting technologies such as incandescent lamps, halogen lamps, xenon lamps, and fluorescent lamps, phosphor-converted white light-emitting diodes (PC-WLEDs) have excellent properties such as low cost, high electro-optical conversion efficiency, high stability and reliability, energy saving, green environmental protection and pollution-free, long life, and easy maintenance, and are widely regarded as the most promising new generation of solid-state lighting sources. In order to obtain a high-performance solid-state lighting source. For the selected phosphor material, it should have the following characteristics: the emission spectrum of the phosphor is concentrated in an appropriate wavelength range, excellent thermal stability and chemical stability, uniform particle distribution and small particle size, high excitation light efficiency and quantum efficiency. Since white light is usually achieved by combining an LED chip with a phosphor, the color rendering index, color temperature, color purity, and color coordinates of white LEDs can be improved by changing the coating thickness of the phosphor and the emission spectrum of the phosphor. The development of phosphors for LEDs has attracted extensive attention and become a research hotspot in recent years.

[0003] However, there are usually three methods for common phosphor-converted WLEDs at present: 1) composed of a blue LED chip and a yellow phosphor; 2) using blue, green, and red phosphors excited by an ultraviolet or near-ultraviolet LED chip; 3) doping two or more activators in the same unit cell to coordinate a single-phase white light phosphor, and coating it on an ultraviolet light-emitting diode chip to achieve phosphor-converted WLEDs. Considering factors such as the current technical situation, processability, and cost, in order to obtain a light-emitting diode with high conversion efficiency, realizing white light through the method of coating an LED chip with a phosphor is still the research focus of countries around the world. Summary of the Invention

[0004] Aiming at the above deficiencies in the existing technology, the main object of the present invention is to provide a sulfur oxide-based phosphor material that can achieve photoluminescence and stress luminescence. This phosphor material has strong thermal stability and fluorescence stability; and the involved preparation method is simple, non-toxic and pollution-free, and the obtained product has high purity; when used as a fluorescence conversion material and applied to the LED field, the obtained solid-state illuminator can exhibit excellent luminous performance, with high light conversion efficiency and luminous intensity.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A sulfur oxide phosphor material, whose chemical formula is Ba 1-1.5x ZnOS:xBi 3+ ; where the doping concentration range of Bi 3+ (i.e., the range of x) is 0.005 - 0.025; the crystal structure belongs to the orthorhombic system.

[0007] Preferably, the value of x is 0.013 - 0.017.

[0008] More preferably, the doping concentration of Bi 3+ (i.e., the value of x) is 0.014 - 0.016. At this time, the chemical formula of this phosphor is Ba 0.9775 ZnOS:0.015Bi 3+ , and this phosphor has strong luminous efficiency. This phosphor has strong absorption peaks in the blue-green visible light band of 400 - 600 nm. When excited by ultraviolet light with a wavelength of 300 - 400 nm, its emission spectrum consists of characteristic emission peaks of Bi 3+ , mainly located in the blue-green region.

[0009] The preparation method of the above sulfur oxide phosphor material includes the following steps:

[0010] 1) Accurately weigh the required raw materials BaCO3, ZnS, and Bi2O3 according to the stoichiometric ratio of Ba 1-1.5x ZnOS:xBi 3+ , where the range of x is 0.005 - 0.025, and the molar mass ratio of BaCO3, ZnS, and Bi2O3 is 1 - 1.5x:1:x / 2;

[0011] 2) Grind the raw materials weighed in step 1), mix them evenly, and then dry the obtained powder;

[0012] 3) Calcinate the powder dried in step 2) under a protective atmosphere, cool it (naturally cool) to room temperature, and then grind it to obtain the sulfur oxide phosphor.

[0013] According to the above scheme, the purities of the raw materials BaCO3, ZnS, and Bi2O3 used are all analytical pure, and the particle size is in the micron or smaller level.

[0014] According to the above scheme, the value of x described in step 1) is 0.005 - 0.025.

[0015] According to the above scheme, the drying temperature described in step 2) is 50 - 80 °C.

[0016] According to the above scheme, the protective atmosphere in step 3) can be selected from argon, nitrogen, etc.; the ventilation flow rate is 20 - 100 Nl / min, and the ventilation duration is from heating to cooling to 250 - 50 °C.

[0017] According to the above scheme, the target temperature of the calcination step in step 3) is 850 - 1000 °C, and the calcination time is 3 - 4 h.

[0018] Furthermore, the calcination step includes: first heating at a rate of 5 - 8 °C / min to 600 - 800 °C, and then continuing to heat at a rate of 4 - 5 °C / min to the target temperature, and holding for 3 - 4 h.

[0019] The present invention relates to the application of the above sulfur oxide phosphor material in LED lighting, wherein the doping concentration of Bi 3+ is 0.5 - 2.5%.

[0020] Specifically, on the basis of the phosphor material prepared with the above-mentioned formula, Eu 3+ ions are co-doped in the formula, and Ba 1-1.5x ZnOS:xBi 3+ is co-doped with Eu 3+ during the preparation process to prepare Ba 1-1.5x-1.5y ZnOS:xBi 3+ , y Eu 3+ ; wherein, x ranges from 0.005 to 0.025, and y ranges from 0.1 to 0.5. By adjusting the doping amount of Eu 3+ in the raw materials, the proportion of Eu 3+ in the obtained reduced phosphor material containing Eu 3+ is changed, so as to shift its emission color.

[0021] Preferably, the x / y is 1:6 - 17.

[0022] Furthermore, the other preparation steps (step 2) and step 3)) of the Ba 1-1.5x-1.5y ZnOS:xBi 3+ , y Eu 3+ phosphor are the same as those of the above sulfur oxide phosphor material.

[0023] In practical applications, by controlling the CIE color coordinate parameters, a phosphor material applicable to white LEDs can be obtained under the excitation of an ultraviolet lamp. The prepared phosphor material has a good single-color emission effect; and it can be co-doped with rare earth ions emitting red light to achieve a single-phase white phosphor in the same matrix, realizing white light emission of LEDs from cold color to warm color, so as to be effectively applied in fields such as white LEDs.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The high-temperature solid-phase reaction method adopted by the present invention can obtain a phosphor with high purity and good luminescence performance through one firing without adding a flux; and the firing temperature involved is relatively low and the calcination time is short; it has good thermal stability and chemical stability; the raw materials involved are easy to obtain and the price is low, and large-scale production can be realized, reducing the production cost.

[0026] 2. The phosphor material of Bi 3+ single-doped sulfur oxide BaZnOS has a relatively wide PL peak near 491 nm; by regulating the heating rate, ventilation duration, etc., a blue-green phosphor with higher luminescence intensity and longer afterglow time is prepared; this blue-green long-afterglow luminescent phosphor can be used as a blue-green component and has potential application value in solid-state lighting devices;

[0027] 3. On the basis of the sulfur oxide phosphor material, the present invention co-dopes Bi 3+ and Eu 3+ into the sulfur oxide, adjusts the concentration ratio and sintering temperature, and can prepare a warm white phosphor with high fluorescence intensity, relatively low correlated color temperature and capable of obtaining warm white light emission under ultraviolet lamp irradiation, which can be used in white LED devices with high luminous efficiency. Description of the Drawings

[0028] Figure 1 SEM diagram of Ba 0.9775 ZnOS:0.015Bi 3+ prepared in Example 3 a and Comparative Example 2 b;

[0029] Figure 2 XRD pattern of the phosphor samples Ba 1-1.5x ZnOS:xBi prepared in Examples 1-5 of the present invention compared with the BaZnOS standard card;

[0030] Figure 3 Linear relationship diagram of the unit cell parameters of the phosphor samples Ba 1-1.5x ZnOS:xBi 3+ prepared in Examples 1-5 of the present invention varying with the doping amount of Bi 3+ ions;

[0031] Figure 4 The phosphor samples Ba 1-1.5x ZnOS:xBi 3+ prepared in Examples 1-5 of the present invention em excitation spectrum measured under an excitation light of λ

[0032] Figure 5 The phosphor samples Ba 1-1.5x ZnOS:xBi 3+ prepared in Examples 1-5 of the present invention ex emission spectrum measured under an excitation light of λ

[0033] Figure 6 Ba 0.9775 ZnOS:0.015Bi 3+ prepared in Example 3 and Comparative Examples 1-3 ex emission spectrum measured under an excitation light of λ

[0034] Figure 7 CIE chromaticity coordinate diagram obtained according to the coordinate markings in Table 2

[0035] Figure 8 The phosphor samples Ba 0.9775 -1.5yZnOS:0.015Bi 3+ , yEu 3+ prepared in Application Examples 1-4 ex emission spectrum measured under an excitation light of λ

[0036] Figure 9 CIE chromaticity coordinate diagram obtained according to the coordinate markings in Table 3 Detailed implementation manners

[0037] The present invention is not limited to the above implementation manners. For those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches are also regarded as within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well known to those of ordinary skill in the art

[0038] In the following examples, the raw materials used were BaCO3 (AR, 99.99%, 0.5 - 1.5 μm), ZnS (AR, 99.99%, 3.3 - 4.3 μm), Bi2O3 (AR, 99.99%, 5.5 - 5.5 μm), Eu2O3 (AR, 99.99%, 4.5 - 5.5 μm).

[0039] Example 1

[0040] A sulfur oxide phosphor material with a chemical formula of Ba 1-1.5x ZnOS:xBi 3+ (x = 0.005), and the specific preparation method is as follows:

[0041] 1) Weigh the required raw materials BaCO3, ZnS, and Bi2O3 accurately according to the stoichiometric ratio of the target chemical formula;

[0042] 2) Place the raw materials in an agate mortar and grind them manually with an agate grinding rod for 15 - 30 min. After mixing evenly, place the obtained powder in an oven (70 °C) to dry;

[0043] 3) Place the powder dried in step 2) in an alumina crucible, then put it into a tube furnace. Under an argon atmosphere (ventilation flow rate is 50 - 80 Nl / min), use a two-stage heating program: in the first stage, heat it to 600 °C at a rate of 8 °C / min, and in the second stage, heat it to 950 °C at a rate of 5 °C / min and keep it calcined for 3 h. Stop ventilation when the temperature drops below 200 °C. After the calcination is completed, cool it to room temperature, and then grind it to obtain a sulfur oxide phosphor (containing Bi Figure 1 phosphor material) with a particle size of 20 - 100 μm (see 3+ a), and its chemical formula is Ba 0.9925 Bi 0.005 ZnOS, which has good single-phase property (see Figure 2 ) and has good monodispersity.

[0044] Example 2

[0045] A sulfur oxide phosphor material, whose preparation method is substantially the same as that of Example 1, except that: the designed doping amount of Bi 3+ is 1% (x = 0.01), and the chemical structural formula formed after the reaction is Ba 0.985 Bi 0.01 ZnOS

[0046] Example 3

[0047] A sulfur oxide phosphor material, whose preparation method is substantially the same as that of Example 1, except that: the designed doping amount of Bi 3+ is 1.5% (x = 0.015), and the chemical structural formula formed after the reaction is Ba 0.9775 Bi 0.015 ZnOS.

[0048] Example 4

[0049] A sulfur oxide phosphor material, whose preparation method is substantially the same as that of Example 1, except that: the designed doping amount of Bi 3+ is 2% (x = 0.02), and the chemical structural formula formed after the reaction is Ba0.9775 Bi 0.02 ZnOS.

[0050] The phosphor obtained in this example was heat-treated at 500 °C for 2 - 3 h (denoted as 2% Bi (heat)), and the results showed that: the crystal structure of the obtained substance was the same as that before heat treatment (see the results in Figure 2 ), and no other impurities were generated, proving that the prepared phosphor has a certain thermal stability.

[0051] Example 5

[0052] A sulfur oxide phosphor material, the preparation method of which is substantially the same as that of Example 1, except that the designed doping amount of Bi 3+ is 2.5% (x = 0.025), and the chemical structural formula formed after the reaction is Ba 0.9775 Bi 0.025 ZnOS.

[0053] The phosphor obtained in this example was heat-treated at 500 °C for 2 - 3 h (2.5% Bi (heat)), and the results showed that: the crystal structure of the obtained substance was the same as that before treatment, and no other impurities were generated, proving that the prepared phosphor has a certain thermal stability.

[0054] Comparative Example 1

[0055] A sulfur oxide phosphor material, the preparation method of which is substantially the same as that of Example 3, except that: in the two-stage heating step, the first stage is heated to 800 °C at a rate of 8 °C / min, and the second stage is heated to 950 °C at a rate of 5 °C / min, and the gas supply is stopped when the temperature is lowered to 300 °C.

[0056] After testing, some oxide impurities such as barium oxide appeared in the obtained phosphor product.

[0057] Comparative Example 2

[0058] A sulfur oxide phosphor material, the preparation method of which is substantially the same as that of Example 3, except that: in the first stage of the calcination process, the temperature is raised to 600 °C at a rate of 6 °C / min, and in the second stage, the temperature is raised to 950 °C at a rate of 5 °C / min and held for 3 h, and the gas supply is stopped when the temperature is lowered to 500 °C.

[0059] After testing, compared with Example 3, the prepared phosphor shows a greater agglomeration phenomenon and lower dispersibility.

[0060] Comparative Example 3

[0061] A sulfur oxide phosphor material, the preparation method of which is substantially the same as that of Example 3, except that: in the first stage, the temperature is raised to 600 °C at a rate of 10 °C / min, and in the second stage, the temperature is raised to 1100 °C at a rate of 5 °C / min and kept for 3 h, and the gas supply is stopped when the temperature is lowered to 300 °C.

[0062] After testing, compared with Example 3, substances such as ZnS and Bi2O3 exist in the prepared phosphor product, resulting in a reduction in the fluorescence effect.

[0063] The powder samples prepared in Examples 1-5 were subjected to qualitative phase analysis using a German Bruker D8 ADVANCE X-ray single crystal diffractometer, and the results are shown in Figure 1 ; It can be observed in the figure that after doping with Bi 3+ The phase analysis results of the product are in good agreement with the BaZnOS standard card, and no other impurity peaks appear, showing good single-phase properties, indicating that Bi 3+ was successfully doped into the BaZnOS lattice.

[0064] Using the Bragg equation and the crystal lattice plane spacing formula as follows

[0065]

[0066]

[0067] The crystal cell parameter changes of the XRD data of the powder samples obtained in Examples 1-5 were calculated (see Table 1). Since the ionic radius of the doped Bi 3+ is slightly smaller than the radius of the substituted ion Ba 2+ , the crystal cell parameters change linearly with the ionic doping amount, which conforms to Vegard's law (see Figure 3 ).

[0068] Table 1 Crystal cell parameters of the phosphor samples Ba 1-1.5x ZnOS:xBi prepared in Examples 1-5

[0069]

[0070] The luminescence properties of the phosphor were monitored using a fluorescence spectrophotometer (model Hitachi F-7000). Under the monitoring of λ ex = 491 nm, an absorption peak at 372 nm can be observed (see Figure 4 ). The above results indicate that the obtained phosphor sample contains Bi 3+ , and the obtained phosphor sample can absorb the photon energy from 372 nm ultraviolet light, thereby inducing the energy level transition of Bi 3+ ions.

[0071] At λ ex= The emission spectra of the powder samples prepared in Examples 1-5 measured under 372 nm excitation light are shown in Figure 5 , and it can be seen that: as the doping concentration of Bi 3+ ions increases, the position and shape of the characteristic emission peak of Bi 3+ ions do not change. A blue-green broadband emission in the wavelength range of 400-600 nm is observed, and the strongest emission peak is located at 491 nm, belonging to the 3+ transition of Bi 3 P 1，0 → 1 S0 energy level. In addition, after turning off the ultraviolet light, the phosphor still exhibits fluorescence within 5-10 s. The fluorescence effect is stronger before 5 s, and after 5 s, the fluorescence phenomenon gradually disappears until it stops emitting light completely.

[0072] By controlling variables such as the heating rate and the ventilation duration, the emission spectra of the powders prepared in Example 3 and Comparative Examples 1-3 measured under λ ex = 372 nm excitation light are analyzed (see Figure 6 ). It can be seen from the figure that: a slower heating rate and a shorter ventilation duration are likely to cause problems such as impurity phases, weakening the fluorescence effect of the obtained phosphor; if the heating rate is too high, impurity phases are also likely to be generated in the fluorescent material, resulting in a change in the crystal field environment, which is not conducive to ensuring the luminescence intensity.

[0073] Using the software CIE1931xy to analyze the CIE coordinates of the powder samples prepared in Examples 1-5 measured under λ ex = 372 nm excitation light (see Table 2), and the CIE chromaticity coordinate diagram obtained by marking the coordinates obtained from Table 2 (see Figure 7 ). As the doping concentration of Bi 3+ ions increases, the above coordinates are all located in the blue-green region, belonging to the characteristic emission light of Bi 3+ . This result indicates that the phosphor sample contains Bi 3+ ions.

[0074] Table 2 CIE chromaticity coordinates of the phosphor samples prepared in Examples 1-5 measured under 372 nm excitation light

[0075]

[0076] On the basis of the phosphor material prepared with the above-mentioned formula, Eu 3+ ions are co-doped in the formula. By adjusting the doping amount of Eu 3+ , a white light-emitting phosphor is coordinated. The designed application examples are as follows:

[0077] Application Example 1

[0078] Based on Example 3, it is applied to the preparation of Bi- and Eu-codoped sulfur oxide phosphor materials for white LEDs. The preparation method is roughly the same as that of Example 3, except that in step 1), 10% Eu is designed to be codoped. 3+ , and the required raw materials BaCO3, ZnS, Bi2O3, and Eu2O3 are accurately weighed according to the stoichiometric ratio of the target chemical formula; the chemical formula formed after the reaction is Ba 0.8275 Bi 0.015 Eu 0.1 ZnOS.

[0079] Application Example 2

[0080] A Bi- and Eu-codoped sulfur oxide phosphor material, the preparation method of which is roughly the same as that of Application Example 1, except that 15% Eu is designed to be codoped. 3+ , and the chemical formula formed after the reaction is Ba 0.7525 Bi 0.015 Eu 0.15 ZnOS.

[0081] Application Example 3

[0082] A Bi- and Eu-codoped sulfur oxide phosphor material, the preparation method of which is roughly the same as that of Application Example 1, except that 20% Eu is designed to be codoped. 3+ , and the chemical formula formed after the reaction is Ba 0.6775 Bi 0.015 Eu 0.2 ZnOS.

[0083] Application Example 4

[0084] A Bi- and Eu-codoped sulfur oxide phosphor material, the preparation method of which is roughly the same as that of Application Example 1, except that 25% Eu is designed to be codoped. 3+ , and the chemical structural formula formed after the reaction is Ba 0.6025 Bi 0.015 Eu 0.25 ZnOS.

[0085] The luminescence properties of the phosphor were monitored using a fluorescence spectrophotometer (model Hitachi F-7000). Under the excitation light of λ ex = 372 nm, a blue-green emission peak of Bi 3+ was observed at 400 - 600 nm for the prepared phosphor. At the same time, a characteristic emission peak of Eu 3+ appeared at 614 nm, belonging to the red light region. As the Eu 3+ concentration increased, the Eu 3+ luminescence enhanced. Due to the energy transfer between Bi and Eu, part of the energy of Bi 3+ was transferred to Eu3+ , resulting in enhanced Eu 3+ emission while Bi 3+ emission decreases (see Figure 8 ).

[0086] Due to the introduction of Eu 3+ ions, a red light component appears in the phosphor. As the Eu 3+ concentration increases, the red light emission is enhanced, the blue-green light is weakened, and the coordination between the red light and the blue light enables the CIE color coordinates of the phosphor to shift from the blue-green light region to the white light region, thus realizing its potential application in white LEDs. The CIE coordinates of the powder samples prepared in Application Examples 1-4 (see Table 3), and the CIE color coordinate diagram obtained by marking the coordinates according to Table 3 (see Figure 9 ).

[0087] Table 3 CIE color coordinates of the phosphor samples prepared in Application Examples 1-4 measured under 372 nm excitation light

[0088]

[0089] The present invention is not limited to the above embodiments. For those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also considered within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well-known to those of ordinary skill in the art.

Claims

1. Application of a sulfur oxide phosphor material as an afterglow material, characterized in that, The chemical formula of the sulfur oxide phosphor material is Ba 1-1.5x ZnOS:xBi 3+ ; where x ranges from 0.005 to 0.025; The preparation steps of the sulfur oxide phosphor material include the following steps: 1) Accurately weigh the required raw materials BaCO3, ZnS, and Bi2O3 according to the stoichiometric ratio of Ba 1-1.5x ZnOS:xBi 3+ ; 2) Grind the weighed raw materials, mix them evenly, and then dry the obtained powder; 3) Calcinate the powder dried in step 2) under a protective atmosphere, cool it to room temperature, and grind it to obtain the sulfur oxide phosphor; The calcination step includes: first heating to 600 - 800 °C at a rate of 5 - 8 °C / min, and then continuing to heat to 850 - 1000 °C at a rate of 4 - 5 °C / min, and holding for 3 - 4 h; During the cooling process, after cooling to 50 - 250 °C, the protective atmosphere is removed.

2. The application according to claim 1, characterized in that, The value of x ranges from 0.013 to 0.

017.

3. The application according to claim 1, characterized in that, In step 3), the ventilation flow rate of the protective atmosphere in the calcination step is 20 - 100 Nl / min, and the calcination time is 3 - 4 h.

4. The application according to claim 1, characterized in that, The particle size of the obtained sulfur oxide phosphor is 20 - 100 μm.

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