CN102304360A - Red divalent bismuth ion doping calcium phosphate fluorescent material and preparation method thereof - Google Patents

Abstract

The present invention provides a kind of preparation method of divalent bismuth ion doped calcium phosphate red fluorescent material, comprises the following steps: the compound raw material containing calcium, phosphorus and bismuth, its molar ratio is calcium:phosphorus:bismuth=2(1-x) :2:2x, where 0.00001≤x≤0.08; pre-fire after grinding and mixing ^{, control temperature at 900-1200 o C} ; Put the sample in a reducing atmosphere at 900-1200 ^o C and react for 15 minutes to 10 hours. The fluorescent material prepared by the method of the present invention has absorption in the ultraviolet and blue spectral regions, and has red fluorescence covering the range of 600nm-750nm under excitation by ultraviolet or blue light, and its fluorescence lifetime is about 10 microseconds; its fluorescence has good thermal quenching characteristics, When the temperature rises from 10K to room temperature, the fluorescence intensity decreases by less than 10%, and the fluorescence lifetime shortens by less than 5%.

Description

Divalent bismuth ion-doped calcium phosphate red fluorescent material and preparation method thereof

technical field

The invention relates to the field of luminescent material research, in particular to a divalent bismuth ion-doped calcium phosphate red fluorescent material and a preparation method thereof.

Background technique

Solid-state LED lighting technology has the advantages of low energy consumption, high luminous efficiency, long service life, mercury-free, small size, and unbreakable, so it is gradually widely used in general lighting, automobiles, transportation, imaging, agriculture, medicine and other fields. According to research from the University of California, Santa Barbara, if traditional light bulbs are replaced with 150 lumens per watt of white LEDs (WLEDs), the United States alone can save $115 billion in lighting by 2025, thus saving 133 buildings. Power stations, saving 258 million tons of greenhouse CO ₂ gas emissions. In view of this, research on LEDs, especially WLEDs, is in the ascendant recently. Among all the schemes based on the combination of LED and phosphor to obtain WLED, the simplest is to combine a blue LED with a yellow phosphor with blue light absorption. The currently commercialized WLED product, the combination of blue InGaN LED and Y ₃ Al ₅ O ₁₂ :Ce ³⁺ (YAG:Ce) (hereinafter referred to as BLED+YAG:Ce), is based on this scheme. The efficiency of this BLED+YAG:Ce product is better than compact fluorescent lamps, but compared with incandescent lamps and halogen lamps (the color temperature is usually 2500-3200K, and the color rendering index CRI is 100), its disadvantage is that the color temperature is relatively high, usually at 4500-6500K; CRI is low, usually less than 80. In order to properly reduce the color temperature of BLED+YAG:Ce, increase its color rendering index (CRI), and obtain warm-toned white LEDs, it is usually necessary to introduce another long-wavelength emitting phosphor, such as red. Newly added luminescent materials usually absorb in the blue region.

Based on this consideration, some Eu ²⁺ , Ce ³⁺ or Mn ²⁺ doped nitrides, oxynitrides, silicates, aluminates and other new fluorescent materials have been reported successively. Among them, nitrides or nitrogen oxides have exceptionally excellent spectral properties, and the quantum efficiency exceeds 70%, and are considered to be the most potential phosphors, so the research on these compounds has been active recently. However, the synthesis of these materials usually requires relatively harsh conditions. For example, Eu ²⁺ doped β-SiAlON needs to be synthesized at 1900 ^o C and 10 atmospheres of nitrogen atmosphere. This kind of high temperature and high pressure places high demands on the equipment. In addition, most of these studies focus on the doping of rare earth ions or transition metal ions, and there are few reports on the doping of divalent bismuth ions Bi ²⁺ .

Contents of the invention

The purpose of the present invention is to address the deficiencies of the prior art, to provide a divalent bismuth ion-doped calcium phosphate fluorescent material and its preparation method, the present invention can be prepared at a lower temperature (≤1200 ^o C), and the cost is lower Bismuth-doped calcium phosphate red phosphor with good resistance to thermal quenching.

The technical scheme adopted to realize the object of the present invention comprises:

A preparation method for divalent bismuth ion-doped calcium phosphate red fluorescent material, comprising the steps of:

(1) Weigh the compound raw materials containing calcium, phosphorus and bismuth, the molar ratio of which is calcium : phosphorus : bismuth = 2(1-x) : 2 : 2x, where 0.00001 ≤ x ≤ 0.08;

(2) After the above-mentioned weighed raw materials are ground and mixed, they are pre-fired at a controlled temperature of 900-1200 ^o C; Temperature 800-1000 ^o C;

(4) Put the fired sample in a reducing atmosphere at 900-1200 ^o C and react for 15 minutes to 10 hours to obtain the desired red fluorescent material.

The calcium-containing compound raw material is any one of calcium carbonate, calcium bicarbonate, calcium oxide, calcium nitrate, calcium oxalate and calcium acetate; the phosphorus-containing compound raw material is ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, Any one of phosphoric acid and phosphorus pentoxide; the bismuth-containing compound raw material is any one of bismuth trioxide, bismuth powder, bismuth subcarbonate and bismuth chloride.

The reducing atmosphere is carbon monoxide, hydrogen or a mixed gas of nitrogen and hydrogen produced by incomplete combustion of graphite powder.

Compared with the prior art, the present invention has the following advantages and beneficial effects: the characteristics of the fluorescent material prepared by the method of the present invention are: (1) under the excitation of ultraviolet light (230-330nm), it has red fluorescence covering the interval of 600nm-750nm; (2) Under the excitation of 350-520nm light, it has red fluorescence covering the range of 600nm-750nm; (3) The lifetime of red fluorescence is about 10 microseconds; (4) Its fluorescence has good thermal quenching characteristics, and the temperature rises from 10K to At room temperature, the fluorescence intensity decreases by less than 10%, and the fluorescence lifetime shortens by less than 5%.

Description of drawings

Fig. 1 is the fluorescence spectrum of bismuth-doped calcium phosphate excited by different wavelengths of blue light in the present invention: the solid line corresponds to the excitation wavelength of 465nm, and the dotted line corresponds to the excitation wavelength of 412nm;

Fig. 2 is the excitation spectrum in the ultraviolet region of bismuth-doped calcium phosphate of the present invention: the solid line corresponds to the emission wavelength of 652nm, and the dotted line corresponds to the emission wavelength of 682nm;

Fig. 3 is the excitation spectrum in the blue light region of bismuth-doped calcium phosphate of the present invention: the solid line corresponds to the emission wavelength of 652nm, and the dotted line corresponds to the emission wavelength of 682nm;

Fig. 4 is the fluorescence decay curve of bismuth-doped calcium phosphate of the present invention, wherein symbol ○ represents the experimental result of emission wavelength 652nm, excitation wavelength 465nm, the black line on this symbol is the fitting result of single exponential decay equation, and the correlation between the two is 99.71 %, the fitted fluorescence lifetime is 8112ns; the symbol ● represents the experimental results of emission wavelength 682nm and excitation wavelength 412nm, the black line on this symbol is the fitting result of single exponential decay equation, the correlation between the two is 99.93%, and the fitting fluorescence lifetime 12498ns;

Fig. 5 is the influence of temperature of the present invention on the fluorescence intensity and the life-span of bismuth-doped calcium phosphate;

Fig. 6 is the fluorescence spectrum of bismuth-doped calcium phosphate at different temperatures in the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with specific examples, but the embodiments of the present invention are not limited thereto, and the process parameters not specifically indicated can be carried out with reference to conventional techniques.

Example 1

Choose calcium carbonate, ammonium dihydrogen phosphate and bismuth trioxide as starting materials, according to the molar ratio of Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.05), that is, Ca : P : Bi = 1.9 : 2 : 0.1, three kinds of raw materials were weighed respectively, and the total weight of the control mixture was 100 grams. 100 grams of the mixture was mixed by ball milling, put into a corundum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 500 ^o C for 10 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1100 ^o C for 10 hours twice, and ground again in the middle. The fired sample was placed in 1100 ^o CH ₂ for 15 minutes to prepare the bivalent bismuth-doped red fluorescent material. X-ray diffraction analysis showed that it was Ca ₂ P ₂ O ₇ pure phase. As shown in Figure 1, this phosphor can produce red fluorescence with a peak at 652nm under excitation at 465nm, and fluorescence with a peak at 682nm under excitation at 412nm. These fluorophores cover the 600-750 nm spectral region. As shown in Figure 2 and Figure 3, the excitation spectrum corresponding to 652nm fluorescence consists of four excitation peaks at 258nm, 280nm, 412nm and 465nm, of which 280nm is the strongest peak; the excitation spectrum corresponding to 682nm fluorescence consists of three excitation peaks at 258nm, 280nm and 465nm Excitation peak composition, of which 258nm is the strongest peak. The lifetimes of 652nm and 682nm fluorescence are 8112ns and 12498ns respectively, as shown in Figure 4. As shown in Figure 5, as the temperature increases, the fluorescence lifetime becomes slightly shorter, the fluorescence intensity slightly weakens, and the fluorescence peak slightly red shifts (see Figure 6). From 10K to 300K, the lifetime is shortened by 5.7%, and the intensity is weakened by 8.1%, which shows that this luminescent material has better resistance to thermal quenching.

Example 2

Choose calcium bicarbonate, ammonium dihydrogen phosphate and bismuth powder as starting materials, according to the molar ratio shown by Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.00001), that is, Ca : P : Bi = 1.99998: 2: 0.00002, take three kinds of raw materials respectively, control mixture gross weight to be 100 grams. 100 grams of the mixture was mixed by ball milling, put into a platinum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 400 ^o C for 10 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1200 ^o C for 5 hours twice, and ground again in the middle. The fired sample was treated in N ₂ +H ₂ at 1200°C for 1 hour to prepare the bivalent bismuth-doped red fluorescent material. X-ray diffraction analysis showed that it was Ca ₂ P ₂ O ₇ pure phase. The spectral properties and thermal quenching resistance of the fluorescent powder are similar to those in Example 1.

Example 3

Choose calcium oxide, ammonium monohydrogen phosphate and bismuth subcarbonate as starting materials, according to the molar ratio of Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.08), that is, Ca : P : Bi = 1.84 : 2: 0.16, three kinds of raw materials are weighed respectively, and the total weight of the control mixture is 100 grams. 100 grams of the mixture was mixed by ball milling, put into a platinum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 800 ^o C for 5 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1100 ^o C for 20 hours twice, and ground again in the middle. The fired sample was placed in incompletely burned graphite powder at 1100 degrees Celsius for 1 hour to prepare a bivalent bismuth-doped red fluorescent material. X-ray diffraction analysis shows that its main phase is Ca ₂ P ₂ O ₇ . The spectral properties and thermal quenching resistance of the fluorescent powder are similar to those in Example 1.

Example 4

Choose calcium oxalate, phosphoric acid and bismuth chloride as starting materials, according to the molar ratio of Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.05), that is, Ca : P : Bi = 1.90 : 2 : 0.10 , take by weighing three kinds of raw materials respectively, and control the total weight of the mixture to be 100 grams. 100 grams of the mixture was mixed by ball milling, put into a platinum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 600 ^o C for 8 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1100 ^o C for 15 hours twice, and ground again in the middle. The fired sample was placed in CO at 1100°C for 4 hours to prepare a bivalent bismuth-doped red fluorescent material. X-ray diffraction analysis shows that its main phase is Ca ₂ P ₂ O ₇ . The spectral properties and thermal quenching resistance of the fluorescent powder are similar to those in Example 1.

Example 5

Choose calcium acetate, phosphorus pentoxide and bismuth trioxide as the starting materials, according to the molar ratio of Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.01), that is, Ca : P : Bi = 1.98 : 2 : 0.02, three kinds of raw materials were weighed respectively, and the total weight of the control mixture was 100 grams. 100 grams of the mixture was mixed by ball milling, put into a platinum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 700 ^o C for 10 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1100 ^o C for 5 hours twice, and ground again in the middle. The fired sample was placed in a nitrogen-hydrogen mixture at 1100 degrees Celsius for 10 hours to prepare a bivalent bismuth-doped red fluorescent material. X-ray diffraction analysis showed that it was Ca ₂ P ₂ O ₇ pure phase. The spectral properties and thermal quenching resistance of the fluorescent powder are similar to those in Example 1.

Example 6

Choose calcium nitrate, phosphorus pentoxide and bismuth powder as starting materials, according to the molar ratio of Ca _2(1-x) P ₂ O ₇ :2xBi (x=0.01), that is, Ca : P : Bi = 1.98 : 2 : 0.02, three kinds of raw materials were weighed respectively, and the total weight of the control mixture was 100 grams. 100 grams of the mixture was mixed by ball milling, put into a platinum crucible, and then put the crucible into a high-temperature electric furnace. Precisely control the heating rate, control the phosphorus compound decomposition reaction speed, prevent the mixture from overflowing from the crucible, and pre-fire the sample at 500 ^o C for 10 hours. The pre-fired samples were taken out, ground and mixed again, put into a crucible, fired at 1100 ^o C for 10 hours twice, and ground again in the middle. The fired sample was treated in CO generated by carbon powder at 1100 degrees Celsius for 0.5 hour, and the divalent bismuth-doped red fluorescent material was obtained. X-ray diffraction analysis showed that it was Ca ₂ P ₂ O ₇ pure phase. The spectral properties and thermal quenching resistance of the fluorescent powder are similar to those in Example 1.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (3)

1. a preparation method of divalent bismuth ion-doped calcium phosphate red fluorescent material, is characterized in that, comprises the steps: (1) Weigh the compound raw materials containing calcium, phosphorus and bismuth, the molar ratio of which is calcium : phosphorus : bismuth = 2(1-x) : 2 : 2x, where 0.00001 ≤ x ≤ 0.08; The above-mentioned weighed raw materials are ground and mixed, and then pre-fired at a temperature of 900-1200 ^o C; (3) The pre-fired samples are taken out, ground and mixed again, and then fired at a high temperature, and the temperature is controlled at 800-1200 o C. 1000 ^° C; (4) Put the fired sample in a reducing atmosphere at 900-1200 ^o C and react for 15 minutes to 10 hours to obtain the desired red fluorescent material. 2. The preparation method according to claim 1, wherein the calcium-containing compound raw material is any one of calcium carbonate, calcium bicarbonate, calcium oxide, calcium nitrate, calcium oxalate and calcium acetate; The phosphorus-containing compound raw material is any one of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, phosphoric acid and phosphorus pentoxide; the bismuth-containing compound raw material is bismuth trioxide, bismuth powder, bismuth subcarbonate and chlorine Any of the bismuth oxides. 3. preparation method according to claim 1, is characterized in that, described reducing atmosphere is the carbon monoxide that graphite powder incomplete combustion produces, the mixed gas of hydrogen or nitrogen and hydrogen.

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