CN104610968B - LED fluorescent powder and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of luminescent materials, and in particular relates to an LED fluorescent powder and a preparation method thereof. The molybdate phosphor is prepared by Al ³⁺ doping modification, and its general formula is Ca _{0.95‑ x} Al _x Tb _0.02 Eu _0.03 MoO ₄ , where x=0.02～0.1. The technological process is: preparation of solution, precipitation reaction, cleaning and drying of precipitation product, sintering of dry product, and sample grinding. During the precipitation reaction, by adjusting the pH value, the raw materials are precipitated at the same time, and the components of the prepared phosphor are evenly distributed and the luminous efficiency is high.

Description

A kind of LED fluorescent powder and preparation method thereof

technical field

The invention belongs to the field of luminescent materials, and in particular relates to an LED fluorescent powder and a preparation method thereof.

Background technique

As a new type of solid-state light source, white LED has the advantages of environmental protection, energy saving, high efficiency and fast response compared with traditional incandescent lamps and fluorescent lamps. It is known as the three major light sources following incandescent lamps, fluorescent lamps and high-pressure gas discharge lamps After the fourth generation of green light source. Since the introduction of InGaN/YAG:Ce white light LED by Nichia Chemical Corporation of Japan in 1996, the research on fluorescent materials for white light LEDs and the exploration of new system materials have quickly become a hot spot in the field of luminescent material research. Phosphor powder, as an important part of white LED, plays an important role in realizing high efficiency and low energy consumption white LED. The molybdate material has the advantages of stable crystal structure, low phonon energy and low preparation temperature, and can effectively absorb violet and blue light, and transfer energy to the rare earth active ions doped in the molybdate matrix. White LED phosphor matrix material with great application prospect. At present, the application of molybdate system phosphors is mainly limited by their low luminous efficiency. Therefore, it is of great significance to study methods to improve the luminous efficiency of molybdate system phosphors. At present, high-temperature solid-state reaction method, hydrothermal method and chemical co-precipitation method are mainly used to prepare phosphors in acid salt system at home and abroad. However, these preparation methods have limitations in one aspect. The high-temperature solid-state reaction method has high sintering temperature, high energy consumption, uneven local structure, and easy to contain impurities, and the particle size distribution obtained by the solid-state reaction method is wide, and the uniformity of the product is difficult to control; the luminescence of the product obtained by the hydrothermal method Weak strength, not suitable for application. Compared with the high-temperature solid-phase method, the chemical precipitation method has the advantages of low sintering temperature, low cost, high purity, and good chemical uniformity. The precipitation is complete and the particles are easy to agglomerate. Therefore, it has become a research focus to explore a technology for preparing molybdate system phosphors that improves luminous efficiency, saves energy, is simple, low-cost, and has no pollution.

Contents of the invention

The object of the present invention is to provide an LED phosphor and a preparation method thereof for the deficiencies of the prior art. By introducing Al ³⁺ into the molybdate fluorescent powder system, the present invention can not only modulate the local crystal field around the rare earth activated ions, improve the luminous efficiency of the fluorescent powder, but also reduce the sintering temperature, control the size of the particles, and make the composition of the particles evenly distributed.

To achieve the above object, the present invention adopts the following technical solutions:

A kind of LED fluorescent powder: said LED fluorescent powder is modified molybdate fluorescent powder prepared by Al ³⁺ doping modification, and its general formula is Ca _0.95-x Al _x Tb _0.02 Eu _0.03 MoO ₄ , wherein x=0.02～0.1; more preferably, x=0.06.

A method for preparing the above-mentioned LED phosphor, comprising the following steps:

(1) Preparation of materials: CaCl ₂ , Na ₂ MoO ₄ 2H ₂ O and AlCl ₃ 6H ₂ O were made into 1mol/L aqueous solution, and Eu ₂ O ₃ and Tb ₃ O ₄ were respectively dissolved in concentrated hydrochloric acid to prepare 0.1mol/L EuCl ₃ and TbCl ₃ solution;

(2) Precipitation reaction: Take CaCl ₂ , AlCl ₃ , EuCl ₃ and TbCl ₃ solutions according to the stoichiometric ratio, mix them into solution A, use NaOH solution to adjust the pH value of solution A to 1-3, and stir evenly; then Add Na ₂ MoO ₄ into solution A, continue to stir for 60-90 minutes at a stirring speed of 400-600 rpm, and obtain a precipitate; adjust the phosphor powder by changing the doping amount of Al ³⁺ ions (2%-10%, molar ratio). The luminous efficiency, and by adjusting the pH value to precipitate different components at the same time, to obtain a precursor with uniform components;

(3) Cleaning and drying of the precipitated product: Centrifuge the precipitate obtained in step (2) with deionized water for 3 to 5 times, and put it in a drying oven to dry;

(4) Sintering of the dried product: put the dried product of step (3) into a box-type high-temperature sintering furnace for roasting;

(5) Grinding the sample: Grinding the sample roasted in step (4) into powder to obtain LED phosphor.

The centrifugation speed in step (3) is 6000-8000 rpm, the drying temperature after centrifugation is 80-90° C., and the drying time is 10-12 hours.

The calcination temperature in step (4) is 700-900° C., the time is 2-4 hours, and the sintering atmosphere is air.

The particle size of the LED fluorescent powder prepared in step (5) is 1-2.5 μm, and the quantum yield is 45%-85%.

The beneficial effects of the present invention are:

(1) The raw materials used in the present invention are abundant, green and environmentally friendly, and the price is low, which reduces the production cost of the fluorescent powder; the process and equipment adopted are simple, easy to implement, easy to operate, and no harmful gas is generated during the preparation process; and in the phosphor powder During the preparation process, by adjusting the pH value, the raw materials can be precipitated at the same time to obtain a precursor with uniform components;

(2) By introducing Al ³⁺ into the molybdate phosphor system, the local crystal field around the rare earth activated ions is modulated, the luminous efficiency of the phosphor is improved, the particle size distribution is uniform, and the particle size is controllable; Changing the doping amount of Al ³⁺ ions within a certain range (2% to 10%) can effectively adjust the luminous efficiency of phosphors, and prepare phosphors with different luminous efficiencies according to actual needs.

Description of drawings

Fig. 1 is the emission spectrum of the fluorescent powder prepared in embodiment 1 and the photoluminescence of the sample;

FIG. 2 is a scanning electron micrograph of the phosphor powder prepared in Example 1. FIG.

detailed description

The present invention further illustrates the present invention with following examples, but protection scope of the present invention is not limited to following examples.

Example 1

The general formula of phosphor powder is: Ca _0.89 Al _0.06 Tb _0.02 Eu _0.03 MoO ₄ , and its preparation process includes the following steps:

1) Firstly, CaCl ₂ , Na ₂ MoO ₄ 2H ₂ O and AlCl ₃ 6H ₂ O were made into 1mol/L aqueous solution, and Eu ₂ O ₃ and Tb ₃ O ₄ were respectively dissolved in concentrated hydrochloric acid to prepare 0.1mol /L of EuCl ₃ and TbCl ₃ solution;

2) Measure and mix CaCl ₂ , AlCl ₃ , EuCl ₃ and TbCl ₃ according to the molar ratio of 89:6:3:2 to form solution A, use NaOH solution to adjust the pH value of solution A to 2, and stir with a magnetic stirrer; Add Na ₂ MoO ₄ to solution A to form a precipitate, and continue magnetic stirring for 60 minutes; centrifuge the obtained precipitate with deionized water for 3 times at a centrifugal speed of 7000 rpm, and dry it in a drying oven at 80°C for 12 hours;

3) Finally, put the dried sample into a box-type high-temperature sintering furnace for sintering at 900°C for 2 hours, and grind it after cooling to obtain phosphor.

The doping amount of Al ³⁺ is 6%, the average particle size of the obtained phosphor particles is 1.5 μm, and the quantum yield is 85%.

Example 2

The general formula of phosphor powder is: Ca _0.85 Al _0.1 Tb _0.02 Eu _0.03 MoO ₄ , and its preparation process includes the following steps:

1) Firstly, CaCl ₂ , Na ₂ MoO ₄ 2H ₂ O and AlCl ₃ 6H ₂ O were made into 1mol/L aqueous solution, and Eu ₂ O ₃ and Tb ₃ O ₄ were respectively dissolved in concentrated hydrochloric acid to prepare 0.1mol /L of EuCl ₃ and TbCl ₃ solution;

2) Measure and mix CaCl ₂ , AlCl ₃ , EuCl ₃ and TbCl ₃ in a molar ratio of 85:10:3:2 to form solution A, use NaOH solution to adjust the pH of solution A to 3, and stir with a magnetic stirrer; Add Na ₂ MoO ₄ to solution A to form a precipitate, and continue magnetic stirring for 90 minutes; centrifuge the obtained precipitate with deionized water for 5 times at a centrifugal speed of 6000 rpm, and dry it in a drying oven at 90°C for 10 hours;

3) Finally, put the dried sample into a box-type high-temperature sintering furnace for sintering at 700°C for 4 hours, and grind it after cooling to obtain phosphor.

The doping amount of Al ³⁺ is 10%, the average particle size of the obtained particles is 1.5 μm, and the quantum yield is 53%.

Example 3

The general formula of phosphor powder is: Ca _0.93 Al _0.02 Tb _0.02 Eu _0.03 MoO ₄ , and its preparation process includes the following steps:

1) Firstly, CaCl ₂ , Na ₂ MoO ₄ 2H ₂ O and AlCl ₃ 6H ₂ O were made into 1mol/L aqueous solution, and Eu ₂ O ₃ and Tb ₃ O ₄ were respectively dissolved in concentrated hydrochloric acid to prepare 0.1mol /L of EuCl ₃ and TbCl ₃ solution;

2) Measure and mix CaCl ₂ , AlCl ₃ , EuCl ₃ and TbCl ₃ in a molar ratio of 93:2:3:2 to form solution A, use NaOH solution to adjust the pH of solution A to 3, and stir with a magnetic stirrer; Add Na ₂ MoO ₄ to solution A to form a precipitate, and continue magnetic stirring for 90 minutes; centrifuge the obtained precipitate with deionized water for 5 times at a centrifugal speed of 6000 rpm, and dry it in a drying oven at 90°C for 10 hours;

3) Finally, put the dried sample into a box-type high-temperature sintering furnace for sintering at 700°C for 4 hours, and grind it after cooling to obtain phosphor.

The doping amount of Al ³⁺ is 2%, the average particle size of the obtained particles is 1.5μm, and the quantum yield is 45%.

comparative example 1

The general formula of phosphor powder is: Ca _0.95 Tb _0.02 Eu _0.03 MoO ₄ , and its preparation process includes the following steps:

1) First make CaCl ₂ , Na ₂ MoO ₄ ·2H ₂ O into 1mol/L aqueous solution, dissolve Eu ₂ O ₃ and Tb ₃ O ₄ in concentrated hydrochloric acid respectively to prepare 0.1mol/L EuCl ₃ and TbCl ₃ solution;

2) Then measure CaCl ₂ , EuCl ₃ and TbCl ₃ according to the molar ratio of 95:3:2 and mix them into solution A, use NaOH solution to adjust the pH value of solution A to 1, stir with a magnetic stirrer; add Na ₂ MoO ₄ A precipitate was formed in solution A, and magnetic stirring was continued for 75 minutes; the obtained precipitate was centrifuged and washed 4 times with deionized water at a centrifugal speed of 8000 rpm, and dried in a drying oven at 85°C for 11 hours to obtain a sample without Al doping;

3) Finally, put the dried sample into a box-type high-temperature sintering furnace for sintering at 800°C for 3 hours, and grind it after cooling to obtain phosphor;

The doping amount of Al ³⁺ is 0%, the average particle size of the obtained particles is 1.5 μm, and the quantum yield is 30%.

By comparing the results of Examples 1-3 with the results of Comparative Example 1, it can be known that when the doping amount of ^Al was 2% to 10%, the quantum yield of the prepared phosphor was 45% to 85%. Compared with the undoped Al sample in Comparative Example 1 (the quantum yield is 30%), the quantum yield is significantly improved, indicating that Al doping is an effective means to improve the luminescent performance of phosphors; more preferably, when Al ³⁺ When the doping amount is 6%, the quantum yield is 85%, and the luminous efficiency of the prepared phosphor is the best.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (6)

1. a LED fluorescent powder, it is characterised in that: described LED fluorescent powder is through Al³⁺The molybdate fluorescent material that doping vario-property prepares, its formula is Ca_0.95-xAl_xTb_0.02Eu_0.03MoO₄, wherein x=0.02～0.1.

LED fluorescent powder the most according to claim 1, it is characterised in that: x=0.06 in described LED fluorescent powder.

3. the method preparing LED fluorescent powder as claimed in claim 1, it is characterised in that: comprise the following steps:

(1) get the raw materials ready: respectively by CaCl₂、Na₂MoO₄·2H₂O and AlCl₃·6H₂O makes the aqueous solution of 1mol/L, by Eu₂O₃And Tb₃O₄It is dissolved in concentrated hydrochloric acid respectively and is configured to the EuCl of 0.1mol/L₃And TbCl₃Solution；

(2) precipitation: stoichiometrically formula ratio measures CaCl₂、AlCl₃、EuCl₃And TbCl₃Solution, is mixed into solution A, and the pH value using NaOH solution regulation solution A is 1～3, stirs；Then by Na₂MoO₄Adding in solution A, continue stirring 60～90min, mixing speed is 400～600 rpm, prepares precipitate；

(3) cleaning of precipitated product and being dried: the precipitate deionized water eccentric cleaning 3 ~ 5 times step (2) prepared, puts in drying baker and is dried；

(4) sintering of desciccate: the product that step (3) is dried is put into box high temperature sintering furnace roasting；

(5) sample grinds: by the sample grind into powder after step (4) roasting, prepares LED fluorescent powder.

The preparation method of LED fluorescent powder the most according to claim 3, it is characterised in that: the centrifugal speed described in step (3) is 6000～8000 rpm, and centrifugal rear baking temperature is 80 ~ 90 DEG C, and drying time is 10-12h.

The preparation method of LED fluorescent powder the most according to claim 3, it is characterised in that: the sintering temperature described in step (4) is 700～900 DEG C, and the time is 2-4 h, and sintering atmosphere is air.

The preparation method of LED fluorescent powder the most according to claim 3, it is characterised in that: the LED fluorescent powder grain diameter obtained by step (5) is 1～2.5 μm, and quantum yield is 45%～85%.