Rare-earth tantalate red luminescent material, preparation method and application thereof

Abstract

The present application relates to a kind of rare earth tantalate red luminescent material, its chemical formula is Li 0.25 Ba 1‑x Eu x Ta 0.75 O3, wherein x=0.09;The preparation method of the luminescent material is: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1‑x Eu x Ta 0.75 O3, x=0.09, Li2CO3, BaCO3, Ta2O5, Eu2O3 are weighed respectively, above-mentioned various raw materials are placed in agate mortar, deionized water is added, grinds, after drying, KCl is added, obtains to be sintered sample;The sintered sample is annealed in crucible using 750 DEG C sintering temperature for 10 hours, the obtained sample is washed with deionized water, after drying, the rare earth tantalate red luminescent material is obtained.The luminescent material has good thermal stability, high luminous intensity, has good color rendering index and higher color purity, the material has the hope to be applied in w-LED.

Description

TECHNICAL FIELD

[0001] The present application relates to the preparation of luminescent materials, in particular to a rare earth tantalate red luminescent material and its preparation method and application. BACKGROUND

[0002] With the development of the times and the progress of science and technology, luminescent materials have become an important strategic resource in today's social life. It is closely related to human life and is widely used in electronic devices, energy, medical treatment, art and other fields, and occupies an irreplaceable position in human daily life. In the field of lighting, due to its low efficiency, traditional lighting such as tungsten lamp, halogen lamp, fluorescent lamp is gradually eliminated, and white light emitting diode (w-LED) mixed with rare earth ion inorganic compound has become a new generation of solid-state lighting device because of its high efficiency, thermal stability, small size, environmental protection and energy saving, color adjustable and other excellent characteristics. The application of solid-state lighting w-LED is also very wide, such as daily lighting in family and office, traffic lighting, instrument and equipment lighting and liquid crystal display (LCD) background light, etc. The more advanced W-LED production method is to combine LED chip with fluorescent powder. The traditional commercial W-LED technology is to coat Y 3-x Ce x Al5O 12 (YAG:Ce 3+ ) yellow fluorescent powder on the top of blue light emitting LED chip to synthesize white light LED. Although this technology has high luminous efficiency and has been widely used, because there is no red light emission in the spectrum, it will lead to the composite w-LED white light being cold, the color rendering index being relatively low (CRI < 80) and the color temperature being relatively high (CCT > 4000K), which can not meet people's demand for high-quality life.

[0003] As people's demand for the quality of lighting is getting higher and higher, and with the development of technology, researchers have improved the LED device. One is to make YAG:Ce 3+The yellow phosphor is red-shifted in the spectrum to increase the red light component in the full spectrum; another way is to dope the system with red light emitting rare earth ions, which can achieve the same purpose; the third is to mix the three primary colors (red, green and blue) phosphor in proportion, which is coated on the ultraviolet (UV) or near ultraviolet (n-UV) LED chip, and high-quality white light with high color rendering index and low color temperature can be achieved. Therefore, finding a red phosphor with excellent luminescent properties is an important way to solve the current problems of w-LED. Generally speaking, the red phosphor applied in LED devices must meet the following three conditions: (1) a wide excitation spectrum; (2) high thermal stability; (3) high luminescent intensity and high quantum efficiency. Since the device will generate heat during operation, if the material applied in the device has poor thermal stability, the quality of the device cannot be effectively guaranteed over time. Therefore, it is challenging to find a red phosphor that meets the above conditions. SUMMARY

[0004] The present application aims to provide a red-emitting rare earth tantalate red luminescent material with high luminescent intensity, good stability and high color purity, as well as a preparation method and application thereof.

[0005] The present application achieves the above-mentioned purpose by the following technical solution: a red-emitting rare earth tantalate luminescent material, which has a chemical formula of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, wherein x = 0.09, and the sintering temperature thereof is 750°C.

[0006] The preparation method of the red-emitting rare earth tantalate luminescent material comprises the following steps

[0007] (1) mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09, Li2CO3, BaCO3, Ta2O5 and Eu2O3 are weighed, and then placed in an agate mortar, deionized water is added, and then ground and dried, and then KCl is added to obtain a sintering sample.

[0008] (2) sintering: the sintering sample is annealed in a crucible at a sintering temperature of 750°C for 10 hours, and then washed with deionized water three times, and then dried in a vacuum oven to obtain the red-emitting rare earth tantalate luminescent material.

[0009] The amount of KCl added is: the molar ratio of KCl to the target product (such as the red-emitting rare earth tantalate luminescent material or the substrate material) is kept at 20:1.

[0010] The application of the rare earth tantalate red luminescent material, the application in the LED device manufacturing.

[0011] The application of the rare earth tantalate red luminescent material, the application in the w-LED device manufacturing.

[0012] Compared with the prior art, the application has the advantages that: the trivalent europium ion (Eu 3+ ) is applied as an activator in the red fluorescent material of the w-LED, by virtue of the excellent 5 D0→ 7 F J (J=1-4) transition, red luminescence is generated, and therefore the inventors of the application apply Eu 3+ as an activator in the red fluorescent material of the w-LED. Meanwhile, the physical and chemical properties of the matrix material are also important bases for obtaining high-quality white light. The tantalate is widely used as a host of rare earth luminescent material, by virtue of the excellent physical and chemical properties,

[0013] occupies a place in the field of inorganic luminescent materials. The tantalate has strong absorption in the near ultraviolet region and can perform energy efficient transmission, and the perovskite structure tantalate is widely used as a host of rare earth luminescent material, due to the high tolerance and diversity of the structure. Therefore, the rare earth doped tantalate fluorescent powder has great research value.

[0014] The rare earth tantalate red luminescent material is prepared by a molten salt method and by regulating a sintering temperature, and the rare earth tantalate red luminescent material Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x=0.09 is prepared at a sintering temperature of 750 DEG C. The x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence characteristics, thermal stability and various parameters of a synthesized device of the material are described in detail. The photoluminescence spectrum shows that there is strong red emission at 614 nm under λex=395 nm. Good color purity and chromaticity coordinate (CIE) characteristics are exhibited. A white light emitting diode (w-LED) device is prepared by using the prepared fluorescent powder, and high-quality color rendering index is shown. The research results show that the Li 3+ Ba 0.25 Eu 1-x Ta x O3, x=0.09 fluorescent powder doped with Eu 0.75 can be used as a potential alternative red fluorescent body of the w-LED. The rare earth tantalate red luminescent material has good thermal stability, high luminescent intensity, good color rendering index and high color purity, and can be effectively excited by near ultraviolet light of 395 nm, and the luminescent material has the potential to be applied in the w-LED. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1are X-ray (XRD) patterns of various samples; wherein, Figure 1 a are XRD patterns of Li 0.25 Ba 1-x Eu x Ta 0.75 O3 samples prepared at sintering temperature of 650 °C - 950 °C. Figure 1 b are XRD patterns of Eu doped luminescent materials Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15.

[0016] Figure 2 are emission and excitation spectra of phosphor samples (i.e. luminescent materials) as shown in Figure 2 wherein, Figure 2 a are excitation spectra of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15 samples prepared at sintering temperature of 750 °C. Figure 2 b are emission spectra of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15 samples prepared at sintering temperature of 750 °C.

[0017] Figure 3 are Li 0.25 Ba 1-x Eu x Ta 0.75 O3 (x = 0.07 - 0.15) phosphors (λ ex = 395 nm) fitted curves of lg I / x versus lg x.

[0018] Figure 4 are Li 0.25 Ba 1-x Eu x Ta 0.75 O3 (x = 0.07, 0.09, 0.13) fluorescence decay curves for 5 D0→ 7 F2 transition.

[0019] Figure 5 are Li 0.25 Ba 1-x Eux Ta 0.75 Emission spectrum of O3 (x=0.09) phosphor as a function of temperature (a) and the relationship between temperature and emission intensity I / I0 (b).

[0020] Figure 6 It is Li 0.25 Ba 1-x Eu x Ta 0.75 Thermal quenching activation energy diagram of O3 (x=0.09) phosphor.

[0021] Figure 7 It is Li 0.25 Ba 1-x Eu x Ta 0.75 Electroluminescence spectrum of O3 (x=0.09) (a), CIE chromaticity coordinates of phosphor and corresponding luminescence image (b).

[0022] Figure 8 The electroluminescence spectrum (a), CIE chromaticity diagram and corresponding emission image (b) of the prepared white LED device.

[0023] Figure 9 The image shows the test report for the red LED.

[0024] Figure 10 This is a test report image for w-LED.

[0025] Figure 11 It is C-LBTO (Li 0.25 Ba 1-x Eu x Ta 0.75 O3) and H-LBTO (LiBa4Ta3O) 12 The crystal structure of ) in which, Figure 11 a and 11b are crystal structure and coordination environment diagrams of C-LBTO; Figure 11 cg is a diagram showing the crystal structure and coordination environment of H-LBTO. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0027] Experimental materials: Li2CO3 (99.99%, Aladdin), BaCO3 (99.95%, Aladdin), Ta2O5 (99.99%, Aladdin), KCl (AR, Xilong Scientific), Eu2O3 (99.99%, Tianjin Fengyue Chemical Co., Ltd.);

[0028] Experimental apparatus: X-ray diffractometer (Germany Bruker Company (D8 Advance)), F-4700 fluorescence spectrometer (Japan Hitachi Company), Varian Cary 500 UV-vis type ultraviolet-visible diffuse reflectance instrument (USA Varian Company).

[0029] Example one: matrix material Li 0.25 BaTa 0.75 O3, and the sintering temperature is 650℃, 750℃, 850℃, 900℃, 950℃ respectively

[0030] (1) mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 BaTa 0.75 O3, Li2CO3, BaCO3 and Ta2O5 are weighed respectively, and then placed in an agate mortar, 2mL of deionized water is added, ground, dried, and then KCl is added to obtain a sintering sample;

[0031] (2) sintering: according to the method described in step (1), several sintering samples are prepared, and the sintering samples are annealed in a crucible at a sintering temperature of 650℃, 750℃, 850℃, 900℃, 950℃ respectively for 10 hours, and then the obtained samples are washed with deionized water for three times, dried in a vacuum oven, and then the corresponding matrix material is obtained.

[0032] Example two: preparation of Eu doped luminescent material, the chemical formula of the luminescent material is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x=0.09, and the sintering temperature is 750℃

[0033] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0034] (1) mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x=0.09, Li2CO3, BaCO3, Ta2O5 and Eu2O3 are weighed respectively, and then placed in an agate mortar, 2mL of deionized water is added, ground, dried, and then KCl is added to obtain a sintering sample;

[0035] (2) sintering: the sintering sample is annealed in a crucible at a sintering temperature of 750℃ for 10 hours, and then the obtained sample is washed with deionized water for three times, dried in a vacuum oven, and then the rare earth tantalate red luminescent material is obtained.

[0036] Referring back to the above method, several samples to be sintered are prepared, and each of the samples to be sintered is annealed in a crucible at a sintering temperature of 850°C and 950°C for 10 hours, respectively. Each of the samples obtained is washed with deionized water for three times, and dried in a vacuum oven, to obtain corresponding other luminescent materials.

[0037] Example Three: Preparation of Eu-doped luminescent material, the chemical formula of which is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x=0.03, and the sintering temperature is 750°C

[0038] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0039] (1) Mixed grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x=0.03, Li2CO3, BaCO3, Ta2O5, and Eu2O3 are weighed, respectively, and placed in an agate mortar, 2 mL of deionized water is added, and grinding is performed. After drying, KCl is added to obtain a sample to be sintered.

[0040] (2) Sintering: according to the method described in step (1), several samples to be sintered are prepared, and each of the samples to be sintered is annealed in a crucible at a sintering temperature of 750°C for 10 hours, respectively. Each of the samples obtained is washed with deionized water for three times, and dried in a vacuum oven, to obtain corresponding luminescent materials.

[0041] Example Four: Preparation of Eu-doped luminescent material, the chemical formula of which is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x=0.05, and the sintering temperature is 750°C

[0042] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0043] (1) Mixed grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75O3, x = 0.05, the molar ratio of each element, Li2CO3, BaCO3, Ta2O5, Eu2O3 are weighed respectively, the above raw materials are placed in an agate mortar, 2 mL of deionized water is added, grinding, drying, then KCl is added to obtain a sintering sample;

[0044] (2) Sintering: according to the method of step (1), several sintering samples are prepared, each sintering sample is annealed at a sintering temperature of 750°C in a crucible for 10 hours, the obtained sample is washed with deionized water for three times, dried in a vacuum oven, and then a corresponding luminescent material is obtained.

[0045] Example Five: Preparation of Eu-doped luminescent material with the chemical formula Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.07, and the sintering temperature is 750°C

[0046] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0047] (1) Mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.07, Li2CO3, BaCO3, Ta2O5, Eu2O3 are weighed respectively, the above raw materials are placed in an agate mortar, 2 mL of deionized water is added, grinding, drying, then KCl is added to obtain a sintering sample;

[0048] (2) Sintering: according to the method of step (1), several sintering samples are prepared, each sintering sample is annealed at a sintering temperature of 750°C in a crucible for 10 hours, the obtained sample is washed with deionized water for three times, dried in a vacuum oven, and then a corresponding luminescent material is obtained.

[0049] Example Six: Preparation of Eu-doped luminescent material with the chemical formula Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.11, and the sintering temperature is 750°C,

[0050] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0051] (1) Mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eux Ta 0.75 O3, x = 0.11, and the sintering temperature is 750°C

[0052] (2) Sintering: according to the method described in step (1), several sintering samples are prepared, each sintering sample is annealed in a crucible for 10 hours at a sintering temperature of 750°C, the obtained sample is washed with deionized water for three times, and dried in a vacuum oven, to obtain the corresponding luminescent material.

[0053] Example Seven: Preparation of Eu-doped luminescent material, the chemical formula of which is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.13, and the sintering temperature is 750°C

[0054] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0055] (1) Mixing and grinding: according to the molar ratio of each element in the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.13, the above various raw materials are placed in an agate mortar, 2 mL of deionized water is added, and grinding is performed, after drying, KCl is added, to obtain a sintering sample;

[0056] (2) Sintering: according to the method described in step (1), several sintering samples are prepared, each sintering sample is annealed in a crucible for 10 hours at a sintering temperature of 750°C, the obtained sample is washed with deionized water for three times, and dried in a vacuum oven, to obtain the corresponding luminescent material.

[0057] Example Eight: Preparation of Eu-doped luminescent material, the chemical formula of which is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.15, and the sintering temperature is 750°C

[0058] The preparation method of the rare earth tantalate red luminescent material comprises the following steps

[0059] (1) Mixing and grinding: according to the molar ratio of each element in the chemical formula Li0.25 Ba 1-x Eu x Ta 0.75 The molar ratio of each element in O3, x = 0.15 was determined by weighing Li2CO3, BaCO3, Ta2O5, and Eu2O3 respectively. All the above raw materials were placed in an agate mortar, 2 mL of deionized water was added, and the mixture was ground and dried. KCl was then added to obtain the sample to be sintered.

[0060] (2) Sintering: According to the method described in step (1), several samples to be sintered are prepared. Each sample to be sintered is annealed in a crucible at 750°C for 10 hours. The obtained samples are then washed three times with deionized water and dried in a vacuum oven to obtain the corresponding luminescent material.

[0061] Example 9: X-ray (XRD) spectra of all samples prepared in Examples 1 to 8 were collected using an X-ray diffractometer. The anode metal used was a Cu target, the X-ray wavelength was 0.154178 nm, and the measurement range was 10°–80° (2θ). Figure 1 As shown, where, Figure 1 a represents the matrix material Li prepared at a sintering temperature of 650℃-950℃ in Example 1. 0.25 Ba 1-x Eu x Ta 0.75 XRD pattern of O3; Figure 1 b is an Eu-doped luminescent material Li prepared at 750℃. 0.25 Ba 1-x Eu x Ta 0.75 XRD patterns of O3 with x = 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, and 0.15;

[0062] like Figure 1 As shown in Figure a: at 650℃, there are many impurities, and the sintering temperature is insufficient; at 750℃, it reacts with Li... 0.25 BaTa 0.75 The O3 standard card matches well; at 850° and 950°, it matches LiBa4Ta3O. 12 The standard card matches well, demonstrating that the synthesized matrix increases with increasing temperature from Li 0.25 BaTa 0.75 The cubic phase O3 gradually transforms into LiBa4Ta3O 12 (H-LBTO) hexagonal phase, but Li will still exist at position 44.05°. 0.25 BaTa 0.75 The (200) crystal plane of O3, but with relatively weaker strength, also proves the transformation of the matrix from cubic to hexagonal phase.

[0063] As Figure 1 b shows: at 750 °C, Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.03 and x = 0.05 samples are mainly cubic phase, compared with Li 0.25 BaTa 0.75 O3pure phase, a small amount of Eu 3+ ion doping, will cause the emergence of hexagonal phase crystal face at 29.38, 43.09 and 53.98 ° position, but the intensity is relatively weak; then with the increase of Eu 3+ concentration (x = 0.07-0.15), Li 0.25 Ba 1- x Eu x Ta 0.75 O3sample gradually converted into cubic phase.

[0064] LiBa4Ta3O 12 , Li 0.25 BaTa 0.75 O3crystal structure is analyzed as follows:

[0065] LiBa4Ta3O 12 (H-LBTO) as a precursor to synthesize BaTaO2N oxynitride, is hexagonal, space group P63mc, α = 90 °, γ = 120 °, The lattice of H-LBTO is composed of TaO6, LiO6 octahedron and BaO 12 tetrahedron, which are coplanar connected. Li 0.25 BaTa 0.75 O3(C-LBTO) is a variant of H-LBTO, with the same chemical composition but different structure, crystallized in P63mc space group, cubic phase, α = 90 °, Because the luminescent properties of the material are closely related to its crystal structure, as an effective control means, crystal phase engineering has been used to design functional luminescent materials. According to the investigation, there are few reports on luminescent materials based on H-LBTO or C-LBTO matrix, and there are almost no applications of LED devices.

[0066] The crystal structures of C-LBTO and H-LBTO are shown in Figure 11 . It can be seen that in both structures, Ta ions are all in six coordination, while Ba ions adopt 12 coordination mode with different deformation degrees. The BaO 12The tetrahedron has four O atoms on each of its two planes, which coordinate with Ba ions. Figure 11 b), but the polyhedron of H-LBTO undergoes a certain degree of twisting, with a BaO6 plane at the center of the polyhedron, and three atoms above and below the plane coordinated with Ba ions (b). Figure 11 dg). Calculate the radius percentage difference (Dr), determined by the following formula for Eu. 3+ Occupation of ions in the LBTO matrix:

[0067]

[0068] Where, r m and r d These represent the matrix cations (Ba) 2+ Or Ta 5+ ions) and substituted ions (Eu) 3+ The radius of ). Where, Ba 2+ Ions and Ta 5+ The Dr values ​​for the ions were 29% and 38%, respectively. Therefore, Eu 3+ Ions can replace Ba in the LBTO host lattice 2+ ion.

[0069] Example 10: The emission and excitation spectra of a phosphor sample (i.e., luminescent material) were measured using a fluorescence spectrometer, such as... Figure 2 As shown. Among them, Figure 2 a represents the sintering temperature of 750℃, Li 0.25 Ba 1-x Eu x Ta 0.75 Excitation spectra of O3 samples with x = 0.03, 0.05, 0.07, 0.09, 0.13, and 0.15. Figure 2 b represents the sintering temperature of 750℃, Li 0.25 Ba 1-x Eu x Ta 0.75 Emission spectra of O3 samples with x = 0.03, 0.05, 0.07, 0.09, 0.13, and 0.15.

[0070] like Figure 2 As shown in Figure a: the broad absorption band of 230-350 nm is formed by the excitation of the matrix (valence band electrons are excited to the conduction band), O 2- →Eu 3+ Charge transfer (CT,O) 2- 2p orbital electrons excited to Eu 3+ (empty 4f orbital) and Eu 3+ of 7 F0→ 5 H3 / 5overlap of H6 electronic transition (-322 nm). It is obvious from the figure that the high concentration of Eu 3+ Doped samples (Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.07-0.15) lower concentration of Eu 3+ Doped samples (Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.03-0.05) blue shift of the wide absorption band, indicating that the sample crystal phase has changed, different crystal structure changes the excitation behavior of Eu 3+ From Figure 2 b we know that 595 nm, 614 nm, excitation peaks belong to Eu 3+ 5 D0→ 7 F1 (magnetic dipole transition), 5 D0→ 7 F2 (electric dipole transition). Magnetic dipole transition is allowed, electric dipole is forbidden.

[0071] According to Dexter theory, the relationship between emission intensity (I) and activator content (x) can be expressed as follows:

[0072] I / x = K [1 + β (X) Q / 3] -1 (2-3)

[0073] In the formula: I is the emission intensity, x is the Eu 3+ doping concentration, β and k are constants, Q = 3, 6, 8, 10 respectively corresponding to exchange interaction, electric dipole-electric dipole, electric dipole-electric quadrupole and electric quadrupole-electric quadrupole interaction. Formula (2-3) can be transformed as:

[0074]

[0075] Example eleven:

[0076] Li 0.25 Ba 1-x Eu x Ta 0.75 O3(x = 0.07-0.15) fluorescent powder (λ ex = 395 nm) lgI / x and lgx fitting curve as Figure 3 shown, through data fitting Q value is 3.51. Therefore, the mechanism of Eu 3+ Concentration quenching is the exchange interaction between ions.

[0077] Example twelve:​

[0078] The fluorescence lifetime data were fitted using Origin software, as shown in Figure 4 The data were fitted well with a bi-exponential function, as follows:

[0079] I(t) = A1 exp(-t / τ1) + A2(-t / τ2) (2-4)

[0080] where A1 and A2 are fitting parameters, I(t) is the luminescence intensity at time t, and τ1 and τ2 are the slow and fast components of the decay lifetime, respectively. The average lifetime of Eu 3+ can be defined as follows:

[0081]

[0082] Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.07 short lifetime (τ2) is 0.09 ms, x = 0.09 is its concentration quenching point, and its short lifetime is 0.24 ms. With the increase of Eu 3+ concentration, its lifetime gradually decreases. When the doping concentration increases, the decrease of lifetime can be attributed to the non-radiative relaxation between Eu 3+ ions. When the doping concentration increases, the average distance of Eu 3+ decreases, which promotes the formation of more Eu 3+ pairs, and the sample has more and more quenching centers, the non-radiative rate increases, resulting in the shortening of its lifetime. In general, the phosphor doped with Eu 3+ shows a long decay time (~ ms), which is due to the forbidden transition of Eu 3+ , usually with a low probability. The results show that the obtained Li 0.25 Ba 1-x Eu x Ta 0.75 O3 phosphor has the potential to show and emit light.

[0083] In order to apply the synthesized material to w-LDE, the thermal stability of the phosphor is very important. Li 0.25 Ba 1-x Eu x Ta 0.75 O3 (λ ex = 395 nm) PL emission spectra at different temperatures are shown in Figure 5 a. When the temperature changes from 300 K to 480 K, the emission intensity can be clearly seen to slowly decrease in the figure, which can be attributed to the thermal quenching effect. Figure 5 The curve in 0.5) is 465 K. When the temperature of the sample is 420 K, which is the working temperature of w-LED, the sample is reduced to 58.6% of the measured intensity. The results show that the prepared Li 0.25 Ba 1-x Eu x Ta 0.75 O3 phosphor has good thermal stability. At the same time, it has the potential to become a substitute red luminescent phosphor for w-LED. In order to further explore the relationship between the emission spectrum intensity and temperature of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 phosphor, the Arrhenius equation can be further understood:

[0084] I = I0 / [1 + A exp(-ΔE / k B T)] (2-6)

[0085] Figure 6 shows the linear relationship of ln[(I0 / I)-1] and 1 / k B T, and the activation energy of Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.09 phosphor is ΔE = 0.20 eV. Generally speaking, the greater the activation energy ΔE, the better the thermal stability of the phosphor.

[0086] Example XIII: Device packaging

[0087] 13.1 Preparation of red LED Raw materials: Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 red phosphor sintered at 750°C; ZWL8820 organic silicone glue. Test instrument: rainbow HP9000;

[0088] LED packaging parameters:

[0089] 395 nm ultraviolet chip packaging:

[0090] 1. Use ZWL8820 organic silicone glue

[0091] 2. The mass ratio of red phosphor to organic silicone glue is 1.8:1

[0092] 3. LED chip: 1 W, ~ 395 nm, San'an Optoelectronics Co., Ltd

[0093] 13.2W LED fabrication

[0094] Raw material: Commercial blue pigment BAM (BaMgAl) 10 O 17 Eu 2+ Shenzhen Looking Long Technology Co., Ltd.; Commercial green powder (Ba,Sr)₂SiO₄:Eu 2+ Shenzhen Looking Long Technology Co., Ltd.; Lithium oxide sintered at 750℃ 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.09 red phosphor; ZWL8820 silicone rubber. Testing instrument: Hongpu HP9000;

[0095] By connecting the 395nm ultraviolet chip doped with a hybrid phosphor BaMgAl 10 O 17 Eu 2+ (BAM:Eu 2+ (Blue), Commercial (Sr, Ba)2SiO4:Eu 2+ (Green) and red phosphor Li prepared at sintering temperature of 750℃ 0.25 Ba 1-x Eu x Ta 0.75 A w-LED device was fabricated using O3 with x = 0.09. The photoluminescence characteristics of the LED were tested using an HP9000 spectrometer driven by a 160mA current and a 3.12V voltage. The correlated color temperature (CCT), color rendering index (CRI), CIE chromaticity coordinates, and luminescence characteristics of the fabricated w-LED were measured.

[0096] The w-LED packaging parameters are as follows:

[0097] 395nm UV chip packaging: Adding commercial blue phosphor BAM and commercial green phosphor (Ba,Sr)2SiO4:Eu 2+ Red fluorescent powder Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09, and the approximate mass ratio of blue, green and red fluorescent powder is 3:1:12. ZWL8820 silicone rubber is used, and the mass ratio of powder to silicone rubber is 1:0.8 (this refers to the total mass of all powders mixed together).

[0098] LED chip: 1 W, ~ 395 nm, San'an Optoelectronics Co., Ltd

[0099] Drying temperature 110 °C, drying time 1 h.

[0100] The packaging method of LED is prior art, therefore the present application does not elaborate the packaging method of LED, only the packaging parameters of LED are disclosed.

[0101] The prepared red LED and w-LED were tested, and the test results are shown in Figure 7 , Figure 8 The test report of red LED and w-LED is shown in Figure 9 , 10 .

[0102] Figure 7 a shows the electroluminescence spectrum of the prepared red LED. Obviously, it has bright red luminescence characteristics, which is consistent with good CIE. Figure 7 b shows the CIE chromaticity diagram of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 red phosphor, and the calculated result is (0.601, 0.317) and is plotted as a point in the figure. Obviously, the color coordinates of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 phosphor are in the red region, and the small figure shows that the phosphor is bright red. In order to further understand the red emission of Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 phosphor, the color purity is calculated:

[0103]

[0104] (x, y) represents the CIE coordinates (x i , y i ) represents the color coordinates of white light, and (x d , y d ) represents the color coordinates of the dominant wavelength point. The main wavelength point can be obtained from the intersection of the connecting point between the equal energy point and the sampling point. The Li 0.25 Ba 1-x Eu x Ta 0.75The color purity of BaTaO3, x = 0.09 is 75.6%. This shows excellent color characteristics. To further confirm the potential application of the prepared red phosphor in white LED, the group of red phosphor with the highest luminous intensity and the best thermal stability (i.e. sintering temperature 750°C, Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09) was coated with commercial blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) and green phosphor ((Ba,Sr)2SiO4:Eu 2+ ) on a 395 nm near-UV LED chip to make a white LED device. Figure 8 a shows the electroluminescence spectra of BaMgAl 10 O 17 :Eu 2+ (BAM:Eu 2+ ) blue phosphor, (Ba,Sr)2SiO4:Eu 2+ green phosphor and red phosphor BaTaO3, x = 0.09 sintered at 750°C, Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09. Figure 8 b shows the color coordinates of the fabricated w-LED. At 160 mA current and 3.12 V voltage, the prepared LED emits bright white light from the phosphor, as can be seen from the small figure. The color coordinates of the final synthesized phosphor are calculated to be (0.298, 0.321), the color temperature is 7445 K, the color rendering index: Ra: 82.4, CRI = 81.2. In summary, the red phosphor BaTaO3, x = 0.09 sintered at 750°C, Li 0.25 Ba 1-x Eu x Ta 0.75 O3, x = 0.09 has good color rendering index and relatively high color purity, which shows that the phosphor has the potential to be applied to w-LED.

[0105] Conclusion

[0106] A new type of red-emitting Li 0.25 BaTa 0.75 O3:Eu 3+ phosphor was synthesized by molten salt method. By adjusting the temperature to control the crystal morphology and luminescent properties, it was finally found that the best sintering temperature was 750°C, and the best Eu doping concentration was 0.09 mol, i.e. the best red-emitting Li 0.25 BaTa 0.75O3:Eu 3+ The phosphor is a sintering temperature of 750℃, and the chemical formula is Li 0.25 Ba 1- x Eu x Ta 0.75 O3, x = 0.09 red phosphor (abbreviation Li 0.25 BaTa 0.75 O3:0.09Eu 3+ phosphor). The excitation spectrum shows that the 395 nm ultraviolet chip can effectively excite Li 0.25 BaTa 0.75 O3:0.09Eu 3+ phosphor. The concentration quenching mechanism can be explained by the energy transfer between ions. The phosphor has good thermal stability, high color purity, and based on the 395 nm ultraviolet chip, Li 0.25 BaTa 0.75 O3 phosphor and good excitation characteristics, and has broad lighting application prospect.

Claims

1. A rare-earth tantalate red luminescent material, characterized in that: Its chemical formula is Li 0.25 Ba 1-x Eu x Ta 0.75 O3, where x = 0.09, the oxidation state of Eu is +3, and its sintering temperature is 750℃; The rare-earth tantalate red luminescent material is prepared by the following method: (1) Mixing and grinding: according to the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 The molar ratios of each element in O3, x = 0.09 were determined. Li2CO3, BaCO3, Ta2O5, and Eu2O3 were weighed separately. These raw materials were placed in an agate mortar, deionized water was added, and the mixture was ground and dried. KCl was then added to obtain the sample to be sintered. (2) Sintering: The sample to be sintered was annealed in a crucible at a sintering temperature of 750℃ for 10 hours. The obtained sample was then washed three times with deionized water and dried in a vacuum oven to obtain the rare earth tantalate red luminescent material.

2. The method for preparing the rare earth tantalate red luminescent material according to claim 1, characterized in that: It includes the following steps: (1) Mixing and grinding: according to the chemical formula Li 0.25 Ba 1-x Eu x Ta 0.75 The molar ratios of each element in O3, x = 0.09 were determined. Li2CO3, BaCO3, Ta2O5, and Eu2O3 were weighed separately. These raw materials were placed in an agate mortar, deionized water was added, and the mixture was ground and dried. KCl was then added to obtain the sample to be sintered. (2) Sintering: The sample to be sintered was annealed in a crucible at a sintering temperature of 750℃ for 10 hours. The obtained sample was then washed three times with deionized water and dried in a vacuum oven to obtain the rare earth tantalate red luminescent material.

3. An application of the rare earth tantalate red luminescent material as described in claim 1, characterized in that: Applications in LED device manufacturing.

4. The application of the rare earth tantalate red luminescent material according to claim 3, characterized in that: Applications in the fabrication of w-LED devices.

Images