CN116396753B - Single-doped nitrogen oxide cold white light fluorescent powder - Google Patents

Abstract

The invention discloses a single doped nitrogen oxide cold white light fluorescent powder, which has a chemical formula of La _4‑xSr₄Si₇N₁₀O₉:xCe³⁺, x is more than 0 and less than or equal to 4. In the invention, the excitation wavelength of the series of fluorescent powder is 200-400 nm, the cold white fluorescent powder with 400-600 nm range is emitted, and the half-peak width of the spectrum is about 110 nm. The series of fluorescent powder has wide emission wavelength range, simple process of the adopted high-temperature solid phase preparation method, easy operation and control, good repeatability, high safety and short preparation time, and is suitable for industrialized mass production and popularization and application.

Description

A single-doped nitrogen oxide cold white light phosphor

Technical Field

The invention belongs to the technical field of luminescent materials, and in particular relates to a single-doped nitrogen oxide cold white light phosphor.

Background technique

As a new generation of lighting source, white light LED is energy-efficient, small in size, and has a long lifespan. Its superior performance makes it have a very broad prospect for research and development and commercial use. The physical and chemical properties of phosphors are stable, and they can match the output wavelength of current commercial LED chips very well. They have a wide emission spectrum in the visible light range, so they have great application potential in the field of lighting devices. First, when using near-ultraviolet chips for excitation, there is no need to consider the color ratio and the color difference caused by different thicknesses of phosphor coatings; secondly, single-matrix white light phosphors do not have the problem of color reabsorption and have a high color rendering index. Therefore, single-matrix white light LED phosphors are the most promising phosphors in the future lighting field and are the first choice as the fourth-generation lighting source.

Nitrogen (oxygen) silicate has good chemical temperature resistance and excellent fluorescence properties. In particular, phosphors based on nitrogen (oxygen) silicate have received more and more attention in the development of phosphors for white light LEDs. Because the prepared products have excellent performance and it is easy to obtain high-brightness rare earth luminescent materials, nitrogen (oxygen) silicate is a luminescent matrix with research potential. At the same time, in recent years, the continuous research on nitrogen (oxygen) silicate phosphors has made great progress, but it is still in the stage of research and development. Therefore, it is of great significance to develop single-doped nitrogen oxide cold white light phosphors.

Summary of the invention

The invention aims to provide a single-doped nitrogen oxide cold white light phosphor and a preparation method thereof.

The technical solution adopted by the present invention is:

The phosphor for solving the above technical problems has a general chemical formula of La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ , wherein 0 ＜ x≤ 4. In addition, since N and O can replace each other to a certain extent, the nitrogen-oxygen ratio under the La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ structure can be expanded to a certain extent, that is, the nitrogen-oxygen ratio is not limited to the general chemical formula, and the fluctuation of the nitrogen-oxygen ratio is also allowed within a certain range of maintaining the structural framework, which is based on the structure characterized by XRD.

The present invention comprises a method for preparing a single-doped nitrogen oxide cold white light phosphor, which is synthesized by a high-temperature solid phase method, and the specific steps are as follows:

(a) According to the molecular formula La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ , where 0 ＜ x ≤ 4; accurately weigh the raw materials LaN (99.0%) or La ₂ O ₃ (99.9%), Sr ₃ N ₂ (99.0%) or SrO (99.9%) or SrCO ₃ (99.9%), Si ₃ N ₄ (99.9%), SiO ₂ (99.99%), CeCl ₃ (99.9%) or CeN (99.9%) or CeO ₂ (99.9%) according to the stoichiometric ratio, fully mix and grind the raw materials in an agate mortar for 20 to 80 min, put the ground mixture into a tungsten crucible, and seal it with a sealing film. The above operations are all completed in a glove box;

(b) The tungsten crucible loaded with the sample is transferred to a high-temperature tube furnace, and the sintering process is carried out in a reducing atmosphere of N ₂ /H ₂ (9:1) at a heating rate of 5 to 10°C/min, sintered at 1300 to 1650°C for 3 to 30 hours, and cooled to room temperature to obtain the sample;

(c) The obtained sintered body is cooled to room temperature and then fully ground to obtain a single-doped nitrogen oxide cold white light phosphor.

In the above preparation method, in the general chemical formula La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ , preferably 0.005 ≤ x ≤ 0.02.

In the above preparation method, a raw material combination of La ₂ O ₃ (99.9%), Sr ₃ N ₂ (99.0%), Si ₃ N ₄ (99.9%) and CeN (99.9%) is preferred.

In the above preparation method, the preferred grinding time is 40 min.

In the above preparation method, it is preferred that the sintering is performed at 1500° C. for 8 hours, and the sintering heating rate is 10° C./min.

In the present invention, Ce ³⁺ is doped into the La ₄ Sr ₄ Si ₇ N ₁₀ O ₉ matrix material, the excitation wavelength is 300-400 nm, and cold white light in the range of 400-600 nm is emitted. The excitation band of the phosphor can be well matched with the near-ultraviolet chip. The series of phosphors have a wide emission wavelength range, and the high-temperature solid-phase preparation method adopted is simple in process, easy to operate and control, good in repeatability, high in safety, and short in preparation time, and are suitable for industrial large-scale production and promotion and application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an X-ray diffraction diagram of a single-doped nitrogen oxide cold white light phosphor prepared in Examples 1 to 6.

FIG. 2 is a series of concentration emission spectra of a single-doped nitrogen oxide cold white light phosphor prepared in Examples 1 to 6.

FIG. 3 is a series of concentration excitation spectra of a single-doped nitrogen oxide cold white light phosphor prepared in Examples 1 to 6.

FIG. 4 is an excitation and emission spectrum diagram of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ prepared in Example 3.

FIG. 5 is a graph showing the quantum efficiency of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ prepared in Example 3.

FIG6 is a fluorescence lifetime decay curve of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ prepared in Example 3 under 360 nm excitation.

FIG. 7 is a temperature-dependent emission spectrum of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ prepared in Example 3 under 360 nm excitation.

Detailed ways

The present invention is further described in detail below in conjunction with the figures and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

According to the stoichiometric ratio of La _3.995 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.005Ce ³⁺ , 1.4285 g of La ₂ O ₃ , 0.8513 g of Sr ₃ N ₂ , 0.7185 g of Si ₃ N ₄ , and 0.0017 g of CeN were weighed, mixed and ground evenly in an agate mortar for about 40 min, the ground powder was placed in a tungsten crucible and sealed, and then the tungsten crucible was placed in a high-temperature tube furnace. The sintering process was carried out in a reducing atmosphere of N ₂ /H ₂ (9:1). The sintering procedure was as follows: heating to 1500 ℃ at a heating rate of 10 ℃/min, sintering at a constant temperature for 8 h, then cooling naturally, and grinding until it dropped to room temperature, to obtain a single-doped nitrogen oxide cold white light phosphor La _3.995 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.005Ce ³⁺ .

Example 2

According to the stoichiometric ratio of La _3.9925 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.0075Ce ³⁺ , 1.4277 g La ₂ O ₃ , 0.8513 g Sr ₃ N ₂ , 0.7185 g Si ₃ N ₄ , and 0.0025 g CeN were weighed, and the other steps were the same as those in Example 1 to obtain a single-doped oxynitride cold white light phosphor La _3.9925 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.0075Ce ³⁺ .

Example 3

According to the stoichiometric ratio of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ , 1.4268 g of La ₂ O ₃ , 0.8513 g of Sr ₃ N ₂ , 0.7185 g of Si ₃ N ₄ , and 0.0034 g of CeN were weighed, and the other steps were the same as those in Example 1 to obtain a single-doped oxynitride cold white light phosphor La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ .

Example 4

According to the stoichiometric ratio of La _3.9875 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.0125Ce ³⁺ , 1.4259 g La ₂ O ₃ , 0.8513 g Sr ₃ N ₂ , 0.7185 g Si ₃ N ₄ , and 0.0042 g CeN were weighed, and the other steps were the same as those in Example 1 to obtain a single-doped oxynitride cold white light phosphor La _3.9875 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.0125Ce ³⁺ .

Example 5

According to the stoichiometric ratio of La _3.985 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.015Ce ³⁺ , 1.4250 g La ₂ O ₃ , 0.8513 g Sr ₃ N ₂ , 0.7185 g Si ₃ N ₄ , and 0.0051 g CeN were weighed, and the other steps were the same as those in Example 1 to obtain a single-doped oxynitride cold white light phosphor La _3.985 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.015Ce ³⁺ .

Example 6

According to the stoichiometric ratio of La _3.98 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.02Ce ³⁺ , 1.4233 g of La ₂ O ₃ , 0.8513 g of Sr ₃ N ₂ , 0.7185 g of Si ₃ N ₄ , and 0.0068 g of CeN were weighed, and the other steps were the same as those in Example 1 to obtain a single-doped oxynitride cold white light phosphor La _3.98 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.02Ce ³⁺ .

The series of single-doped nitrogen oxide cold white light phosphors obtained in Examples 1 to 6 were subjected to XRD analysis, see Figure 1. The obtained material was single-phase and all diffraction peaks matched the standard card, indicating that the prepared phosphor was pure phase and Ce ³⁺ successfully entered the matrix lattice while maintaining the crystal structure unchanged.

The luminescence performance of the series of single-doped nitrogen oxide cold white light phosphors obtained in Examples 2 to 8 was tested by fluorescence spectrometer, i.e., the excitation emission spectrum, see Figures 2 and 3. The excitation spectrum shows that the excitation range of the compound is 200-400nm, with a main peak at 360nm; the emission spectrum shows that under 360nm wavelength excitation, the emission spectrum range is 400-600nm, and the main emission peak red-shifts from 436nm to 462nm as the Ce ³⁺ doping concentration increases. When the Ce ³⁺ doping concentration is x = 0.01, the fluorescence intensity is the maximum.

The phosphor prepared in Example 3 was tested for excitation and emission spectra, see Figure 4. The excitation spectrum shows that the phosphor can effectively absorb near-ultraviolet light of 200 to 400 nm, so that it can match the near-ultraviolet LED chip; it emits 400 to 600 nm orange light under near-ultraviolet 360nm excitation, with a peak at 440 nm. Its emission originates from the 5d→4f transition of Ce ³⁺ , and its spectrum half-peak width is about 110 nm, which belongs to wide-spectrum cold white light emission.

The La _3.99 Sr ₄ Si ₇ N _{10 O 9} : 0.01Ce ³⁺ phosphor prepared in Example ³ has an internal quantum efficiency of 7.10% under near _{- ultraviolet light} excitation of 360 _nm wavelength, see FIG5 .

The La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ phosphor prepared in Example _{3 has} ^{an average fluorescence lifetime of 4.825 nanoseconds under 360 nm ultraviolet light excitation, and the lifetime curve shows a multi-exponential fitting, indicating that Ce 3+} _{occupies multiple crystallographic} ^sites , see Figure 6.

The emission spectra of La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ obtained in Example 3 at different temperatures under 360 nm excitation are shown in Figure 6. As the temperature gradually increases from 298 K to 498 K, the relative intensity of the La _3.99 Sr ₄ Si ₇ N ₁₀ O ₉ : 0.01Ce ³⁺ phosphor gradually decreases. The main peak position hardly drifts, indicating that it has good anti-color drift performance at high temperatures.

Since La3+ and Ce3+ are equivalent and have similar atomic radii, many compounds containing La and Ce have isomorphic structures. In this article, only samples with smaller doping concentrations are selected, and the protection scope is not limited to the above embodiments, and La _{4- x} Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ , where 0 ＜ x ≤ 4, the range of which can be achieved.

Claims (5)

1. A single-doped nitrogen oxide cold white light phosphor, characterized in that: the chemical formula is La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ :xCe ³⁺ , 0＜ x ≤ 0.02. 2. The single-doped nitrogen oxide cold white light phosphor according to claim 1 is characterized in that: the excitation wavelength is 200-400 nm, the emission wavelength is 400-600 nm, the spectrum half-peak width is 110 nm, and it belongs to cold white light emission. 3. The method for preparing a single-doped nitrogen oxide cold white light phosphor according to claim 1 is characterized by adopting a high temperature solid phase method, and the specific steps are as follows: (a) According to the molecular formula La _4-x Sr ₄ Si ₇ N ₁₀ O ₉ : xCe ³⁺ , wherein 0＜ x ≤ 0.02; accurately weigh the raw materials LaN with a purity of 99.0% or La ₂ O ₃ with a purity of 99.9%, Sr ₃ N ₂ with a purity of 99.0% or SrO with a purity of 99.9% or SrCO ₃ with a purity of 99.9%, Si ₃ N ₄ with a purity of 99.9%, CeCl ₃ with a purity of 99.9% or CeN with a purity of 99.9% or CeO ₂ with a purity of 99.9% according to the stoichiometric ratio, fully mix the raw materials in an agate mortar and grind them for 20 to 80 min, put the ground mixture into a tungsten crucible, and seal it with a sealing film. The above operations are all completed in a glove box; (b) The tungsten crucible loaded with the sample is transferred to a high-temperature tube furnace, and the sintering process is carried out in a reducing atmosphere of _N2 / _H2 with a volume ratio of 9:1, with a heating rate of 5-10°C/min, sintering at 1300-1650°C for 3-30 hours, and cooling to room temperature to obtain the sample; (c) The obtained sintered body is cooled to room temperature and then fully ground to obtain a single-doped nitrogen oxide cold white light phosphor. 4. The method for preparing a single-doped nitrogen oxide cold white light phosphor according to claim 3, characterized in that the raw materials are a _{combination of La2O3} with a purity of 99.0%, _Sr3N2 with a purity of 99.0%, _Si3N4 with a purity of _99.9 % and CeN with a purity of 99.9%. 5. The method for preparing a single-doped nitrogen oxide cold white light phosphor according to claim 3, characterized in that: the grinding time is 40 min; the sintering is performed at 1500°C for 8 hours, and the sintering heating rate is 10°C/min.