CN106433641B - A kind of method that low heat temperature solid state reaction prepares rear-earth-doped calcium stannate fluorescent material - Google Patents

Abstract

The invention discloses a method for preparing a rare earth-doped calcium stannate fluorescent material by a low-temperature solid-state reaction method. The method is to mix and ball-mill tin sources, carbon powder, calcium sources and rare earth oxides, form agglomerates, and dry; The block material is placed in a mixed atmosphere containing CO and CO ₂ for one roasting, and then placed in an atmosphere containing O ₂ for a second roasting to obtain a rare earth-doped calcium stannate fluorescent material; this method is different from the traditional high-temperature solid phase Compared with the method of preparing the rare earth-doped stannate fluorescent material by the reaction method, the calcination temperature is low, the calcination time is short, and the fluorescent performance of the product is better.

Description

A method for preparing rare earth-doped calcium stannate fluorescent material by low-temperature solid-state reaction method

technical field

The invention relates to a preparation method of a rare earth-doped calcium stannate fluorescent material, in particular to a method for preparing a rare earth-doped calcium stannate fluorescent material by a low-temperature solid-state reaction method, and belongs to the field of fluorescent material preparation.

Background technique

A substance absorbs light of a certain wavelength and immediately emits light of a different wavelength, which is called fluorescence. When the incident light disappears, the fluorescent material will immediately stop emitting light. More precisely, fluorescence refers to some fairly bright colors of light seen by the human eye under external light, such as green, orange, and yellow. People often call them neon lights. Fluorescent materials are mainly divided into inorganic and organic fluorescent materials. Organic fluorescent materials have defects such as refractory degradation, easy to cause secondary pollution, and carcinogenicity. Inorganic fluorescent materials have strong light absorption ability and high conversion rate, and are easy to realize industrial production.

The energy of persistent luminescent materials mainly comes from two aspects, absorbing ultraviolet and visible light, and then releasing visible light in the form of light waves. This persistent luminescent material has been widely used in many fields, such as emergency lighting, display, image storage and safety indication. The main components of the current commercial fluorescent materials are SrAl ₂ O ₄ : Eu ²⁺ , Dy ³⁺ (green), CaAl ₂ O ₄ : Eu ²⁺ , Nd ³⁺ (blue) and Y ₂ O ₂ S : Eu ^{3 +} , Ti4 ⁺ , Mg ²⁺ (red). However, there are some disadvantages, such as poor chemical stability of sulfide and easy moisture decomposition.

Rare earth elements have luminescent properties because of their unique outer electronic structure. The electronic configuration of rare earth metal atoms can be written as: 1s ² 2s 2 ^{2p 6} 3s ² 3p ⁶ 3d ¹⁰ 4s ^{2 4p 6 4d 10} 4f ⁿ 5s ² 5p ⁶ 5d ^m 6s ² , where n=1-14, m=0 or 1. Rare earth elements have an incompletely filled 4f layer, and their luminescent properties come from this electronic configuration. The excitation and emission of rare earth metal ions are mainly manifested in the following three ways: (1) transition between 4f energy levels; (2) 4f and Transition between 5d energy levels: (3) Charge transfer state transition (4fn-4f ⁿ⁺¹ L ^-1 , L=ligand).

Calcium stannate CaSnO ₃ has a perovskite structure and stable properties. At the same time, the perovskite type is used as a carrier, and the doped rare earth ions are very easy to implant into the lattice, and create a trap depth in a suitable place, which can store excitation energy. And after emitting light, reactivate at room temperature. In addition, calcium stannate has stable physical and chemical properties compared with sulfide, does not pollute the environment, has low processing cost, and is simple to synthesize. Therefore, calcium stannate can be used as a fluorescent material, and will be more commercially used.

At present, the main methods for preparing fluorescent materials by rare earth doped calcium stannate include high-temperature solid-state reaction method and wet chemical synthesis method. The high-temperature sintering method mostly uses SnO ₂ , CaCO ₃ and rare earth oxides as raw materials, and the sintering temperature is as high as 1300-1600°C, but the product has problems such as poor uniformity and uneven crystal structure. Wet synthesis is to prepare soluble calcium salt and tin salt (mainly nitrate and chloride salt) into a solution according to the ratio, and then adjust the pH of the solution to obtain the precursor of hydroxyl precipitation. After washing, the temperature is about 800 ℃ for dehydration, Roasting, the final product is obtained. The wet process can obtain rare earth-doped calcium stannate fluorescent material particles with uniform particle size and stable properties, but there are problems such as low yield and long process flow, and it is only in the laboratory research stage.

Therefore, it is of great significance to develop a method for preparing rare earth-doped calcium stannate fluorescent materials by a low-temperature calcination method.

Contents of the invention

In view of the deficiencies in the existing high-temperature solid-phase sintering method for preparing rare-earth-doped calcium stannate fluorescent materials, the purpose of the present invention is to provide a rare-earth-doped calcium stannate with low calcination temperature and short time, which has a uniform and stable synthetic crystal phase structure. A method for calcium stannate fluorescent material, which is more conducive to industrial production.

In order to achieve the above-mentioned technical purpose, the present invention provides a method for preparing rare earth-doped calcium stannate fluorescent material by a low-temperature solid-state reaction method. block, drying; the obtained dry block is first placed in a mixed atmosphere containing CO and CO ₂ , and roasted once at a temperature of 850-950°C, and then placed in an atmosphere containing O ₂ , and baked a second time at a temperature of 900-1000°C Roasting; the rare earth-doped calcium stannate fluorescent material is obtained.

The key of the technical scheme of the present invention adopts two stages of roasting under different atmosphere conditions. After a long period of extensive experimental research, it has been shown that: in the process of one stage of roasting, under the joint activation of carbon powder in a mixed atmosphere containing CO and _CO , the oxidation The reactivity of tin is greatly enhanced. At the same time, adding a small amount of stannous oxide and metal tin to tin dioxide can further improve the reactivity of tin during roasting. This kind of tin source is more likely to react with calcium source, especially During the solid-phase reaction, the migration speed of rare earth ions is accelerated, and it is easier to dope into the perovskite-type calcium stannate lattice to form a stable doped crystal phase; in the second-stage roasting process, the oxidation reaction is mainly carried out, so that The divalent tin ions that may exist in the crystal phase are fully oxidized to ensure product stability and purity. Through the method of the invention, the temperature in the whole preparation process can be controlled below 1000 DEG C, and the synthesis time is shortened to 90-210 minutes.

In a preferred scheme, the molar ratio of tin and calcium in the tin source and the calcium source is 1:1.

In a preferred solution, the molar weight of the carbon powder is 0.1-1% of the total molar weight of tin and calcium in the tin source and the calcium source.

In a preferred solution, the rare earth oxide is 0.5-3% of the total molar weight of tin and calcium in the tin source and the calcium source.

More preferably, the tin source is composed of tin dioxide, tin protooxide and/or metallic tin.

More preferably, the molar percentage of tin dioxide in the tin source is 89-99%.

More preferably, the calcium source is calcium carbonate and/or calcium oxide.

In a preferred solution, the carbon powder is activated carbon powder.

More preferably, the rare earth oxides include lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide , lutetium oxide, scandium oxide, yttrium oxide at least one.

In a preferred scheme, the mixed atmosphere containing CO and CO ₂ includes the following volume percentage components: CO 5-15%; CO ₂ 45-85%; N ₂ ≤50% (0-50%).

In a preferred solution, the O ₂ -containing atmosphere includes the following volume percentage components: O ₂ 15-50%; N ₂ 50-85%.

In a preferred scheme, the one-stage roasting time is 30-90 minutes.

In a preferred scheme, the second-stage calcination time is 60-120 minutes.

In a preferred solution, ball milling is performed until 100% of the particle size of the mixed material is less than -0.045mm.

In a preferred solution, the calcined product is cooled to room temperature under a protective atmosphere. The protective atmosphere generally refers to nitrogen or inert gas and their combination. Such as _N2 and/or Ar.

Compared with the prior art, the beneficial technical effect brought by the technical solution of the present invention:

1) The biggest advantage of the technical solution of the present invention is that it greatly reduces the reaction temperature in the process of preparing the rare earth-doped calcium stannate fluorescent material by solid-state reaction, shortens the reaction time, makes the reaction temperature milder, and achieves the purpose of energy saving and cost reduction . The traditional solid-state reaction synthesis of rare earth-doped calcium stannate fluorescent materials has a stable property of tin dioxide, with a melting point as high as 1630°C, and it is difficult to react with other substances at low temperatures. SnO ₂ , CaCO ₃ and rare earth oxides are used as raw materials. The temperature is as high as 1300-1600°C and the reaction rate is slow; however, in the technical solution of the present invention, the temperature is controlled below 1000°C during the entire synthesis process, and the synthesis time is shortened to 90-210 minutes, which is beneficial to industrial production.

2) The rare earth-doped calcium stannate fluorescent material prepared by the technical solution of the present invention has good crystal structure uniformity, stable properties and good fluorescent performance. It overcomes the problems of poor uniformity, non-uniform crystal structure and poor fluorescent performance of the rare earth-doped calcium stannate fluorescent material synthesized by the traditional solid-state method.

Description of drawings

[Fig. 1] is the product XRD spectrum of embodiment 1.

[Fig. 2] is the product XRD spectrum of Comparative Example 1.

[Fig. 3] is the product XRD spectrum of comparative example 2.

[ FIG. 4 ] is the fluorescence spectrum of Example 1 and Comparative Examples 1 and 2.

Detailed ways

The following examples are intended to further illustrate the content of the present invention, rather than limit the protection scope of the claims of the present invention.

Example 1

Mix tin dioxide, stannous oxide, metal tin, active carbon powder, calcium carbonate, calcium oxide, and europium oxide uniformly according to a certain ratio, wherein the ratio of tin dioxide, stannous oxide, and metal tin powder is 89mol%: 10mol%: 1mol%, the ratio of calcium carbonate and calcium oxide is 50mol%:50mol%, the ratio of tin-calcium elements is 1:1, the amount of activated carbon powder is 0.1mol% of the total amount of tin-calcium, and the ratio of europium oxide is 0.5% of the total molar amount of tin-calcium mol%, the above materials are mixed and ball milled until the particle size is 100% less than -0.045mm. Then add 8.5% water to make agglomerates. After drying, place the dry agglomerates in a CO-CO ₂ -N ₂ atmosphere for a period of calcination. The gas ratio is 5%:45%:50%, and the calcination temperature is 850°C. , the calcination time is 90min, the ratio of O ₂ -N ₂ in the second-stage calcination atmosphere is 50%:50%, the calcination temperature is 1000°C, and the calcination time is 120min. , by XRD quantitative analysis, the calcium stannate content of the product reaches 98.7%. The XRD pattern of the product is shown in Figure 1. There is only calcium stannate in the product, and no diffraction peak of europium oxide is found.

Comparative Example 1

Mix tin dioxide, calcium carbonate, and europium oxide evenly according to a certain ratio. The ratio of tin to calcium is 1:1, and the ratio of europium oxide is 0.5mol% of the molar weight of tin to calcium. Mix the above materials and ball mill until the particle size is 100% less than -0.045mm. Then add 8.5% water to make agglomerates. After drying, put the dry agglomerates into _N2 atmosphere for roasting. The roasting temperature is 1350°C and the roasting time is 300min. After the samples are cooled and taken out, the rare earth europium-doped stannic acid is obtained. The calcium fluorescent material is quantitatively analyzed by XRD, and the calcium stannate content of the product is 96.2%. The XRD diagram of the product is shown in Figure 2.

Comparative Example 2

Mix tin dioxide, activated carbon powder, calcium carbonate, calcium oxide, and europium oxide evenly according to a certain ratio, wherein the ratio of calcium carbonate and calcium oxide is 50mol%:50mol%, the ratio of tin to calcium is 1:1, and the amount of activated carbon powder is 0.1 mol% of the total amount of tin-calcium, and the proportion of europium oxide is 0.5 mol% of the molar amount of tin-calcium. The above materials are mixed and ball milled until the particle size is 100% less than -0.045mm. Then add 8.5% water to make agglomerates. After drying, place the dry agglomerates in a CO-CO ₂ -N ₂ atmosphere for a period of calcination. The gas ratio is 5%:45%:50%, and the calcination temperature is 850°C. , the calcination time is 90min, the ratio of O ₂ -N ₂ in the second-stage calcination atmosphere is 50%:50%, the calcination temperature is 1000°C, and the calcination time is 120min. , through XRD quantitative analysis, the calcium stannate content of the product reaches 92.7%.

Comparative Example 3

Mix tin dioxide, calcium carbonate, and europium oxide evenly according to a certain ratio. The ratio of tin to calcium is 1:1, and the ratio of europium oxide is 0.5mol% of the molar weight of tin to calcium. Mix the above materials and ball mill until the particle size is 100% less than -0.045mm. Then add 8.5% water to make agglomerates. After drying, put the dry agglomerates into _N2 atmosphere for roasting. The roasting temperature is 1000°C and the roasting time is 300min. After the samples are cooled and taken out, rare earth europium-doped stannic acid is obtained. The calcium fluorescent material is quantitatively analyzed by XRD, and the calcium stannate content of the product is 6.2%. The XRD diagram of the product is shown in Figure 3.

The XRD spectrum of the sample of embodiment 1 and comparative example 1 and 3 can be found, the present invention can obtain the high-purity calcium stannate product in the reaction temperature that reduces, and conversion rate is high, and reaction time is short, is conducive to the doping of rare earth element miscellaneous.

The samples of Example 1 and Comparative Examples 1 and 2 were subjected to fluorescence analysis, and the excitation spectrum and emission spectrum of the samples were obtained respectively. It can be seen that the fluorescence performance of the product obtained by the present invention is much higher than that of the tin prepared by the conventional high-temperature roasting method of Comparative Example 1. Calcium acid fluorescent material, the product performance of the present invention is superior.

Example 2

Mix tin dioxide, stannous oxide, metallic tin, activated carbon powder, calcium carbonate, calcium oxide, and thulium oxide uniformly according to a certain ratio, wherein the ratio of tin dioxide, stannous oxide, and metallic tin powder is 99mol%:0mol%: 1mol%, the ratio of calcium carbonate and calcium oxide is 100mol%:0mol%, the ratio of tin-calcium element is 1:1, the amount of activated carbon powder is 1mol% of the total amount of tin-calcium, and the ratio of europium oxide is 1mol% of the molar amount of tin-calcium, Mix the above materials and ball mill until the particle size is 100% less than -0.045mm. Then add 8.2% water to make agglomerates. After drying, place the dry agglomerates in a CO-CO ₂ -N ₂ atmosphere for a period of calcination. The gas ratio is 15%:85%:0%, and the calcination temperature is 950°C. , the calcination time is 30min, the ratio of O ₂ -N ₂ in the second-stage calcination atmosphere is 50%:50%, the calcination temperature is 900°C, and the calcination time is 60min. , by XRD quantitative analysis, the content of calcium stannate in the product reaches 99.1%.

Example 3

Mix tin dioxide, stannous oxide, metallic tin, activated carbon powder, calcium carbonate, calcium oxide, and terbium oxide uniformly according to a certain ratio, wherein the ratio of tin dioxide, stannous oxide, and metallic tin powder is 90mol%: 10mol%: 0mol%, the ratio of calcium carbonate and calcium oxide is 0mol%:100mol%, the ratio of tin-calcium elements is 1:1, the amount of activated carbon powder is 0.6mol% of the total amount of tin-calcium, and the ratio of europium oxide is 3mol% of the molar amount of tin-calcium , Mix the above materials and ball mill until the particle size is 100% less than -0.045mm. Then add 8.6% water to make agglomerates. After drying, place the dry agglomerates in a CO-CO ₂ -N ₂ atmosphere for a period of calcination. The gas ratio is 10%:75%:15%, and the calcination temperature is 900°C. , the calcination time is 60min, the ratio of O ₂ -N ₂ in the second-stage calcination atmosphere is 15%:85%, the calcination temperature is 950°C, and the calcination time is 60min. , through XRD quantitative analysis, the calcium stannate content of the product reaches 99.2%.

Example 4

Mix tin dioxide, stannous oxide, metallic tin, activated carbon powder, calcium carbonate, calcium oxide, and dysprosium oxide evenly in a certain proportion, wherein the ratio of tin dioxide, stannous oxide, and metallic tin powder is 95mol%:4.5mol% : 0.5mol%, the ratio of calcium carbonate and calcium oxide is 37mol%: 63mol%, the ratio of tin-calcium elements is 1:1, the amount of activated carbon powder is 0.8mol% of the total amount of tin-calcium, and the ratio of europium oxide is 1% of the molar amount of tin-calcium 0.9mol%, the above materials are mixed and ball milled until the particle size is 100% less than -0.045mm. Then add 8.6% water to make agglomerates, and after they are dried, put the dry agglomerates into a CO-CO ₂ -N ₂ atmosphere for a period of calcination, the gas ratio is 10%:55%:35%, and the calcination temperature is 925°C , the calcination time is 60min, the ratio of O ₂ -N ₂ in the second-stage calcination atmosphere is 25%:75%, the calcination temperature is 900°C, and the calcination time is 120min. , through XRD quantitative analysis, the calcium stannate content of the product reaches 99.2%.

Claims (9)

1. a kind of method that low heat temperature solid state reaction prepares rear-earth-doped calcium stannate fluorescent material, it is characterised in that：By tin source, charcoal After powder, calcium source and rare earth oxide mixing and ball milling, agglomeration, drying；Gained drying block is first placed in containing CO and CO₂Mixed atmosphere In, it is once roasted at a temperature of 850~950 DEG C, then be placed in containing O₂In atmosphere, two are carried out at a temperature of 900~1000 DEG C Secondary roasting；Up to rear-earth-doped calcium stannate fluorescent material；The tin source is by stannic oxide and stannous oxide and/or metallic tin group At；The mole percent level of stannic oxide is 89~99% in the tin source.

2. the method that low heat temperature solid state reaction according to claim 1 prepares rear-earth-doped calcium stannate fluorescent material, special Sign is：

The molar ratio of tin and calcium is 1 in the tin source and calcium source:1；

The mole of the powdered carbon is 0.1~1% of the integral molar quantity of tin and calcium in tin source and calcium source；

The rare earth oxide is 0.5~3% of the integral molar quantity of tin and calcium in tin source and calcium source.

3. the method that low heat temperature solid state reaction according to claim 1 or 2 prepares rear-earth-doped calcium stannate fluorescent material, It is characterized in that：The calcium source is calcium carbonate and/or calcium oxide.

4. the method that low heat temperature solid state reaction according to claim 1 or 2 prepares rear-earth-doped calcium stannate fluorescent material, It is characterized in that：The rare earth oxide includes lanthana, cerium oxide, praseodymium oxide, neodymia, promethium oxide, samarium oxide, oxidation In europium, gadolinium oxide, terbium oxide, dysprosia, holimium oxide, erbium oxide, thulium oxide, ytterbium oxide, luteium oxide, scandium oxide, yttrium oxide extremely Few one kind.

5. the method that low heat temperature solid state reaction according to claim 1 prepares rear-earth-doped calcium stannate fluorescent material, special Sign is：Described contains CO and CO₂Mixed atmosphere includes following volumes percent composition：

CO 5~15%；

CO₂45~85%；

N₂≤ 50%.

6. the method that low heat temperature solid state reaction according to claim 1 prepares rear-earth-doped calcium stannate fluorescent material, special Sign is：Described contains O₂Atmosphere includes following volumes percent composition：

O₂15~50%；

N₂50~85%.

7. the method that low heat temperature solid state reaction according to claim 1 prepares rear-earth-doped calcium stannate fluorescent material, special Sign is：Roasting time is 30~90min.

8. the method that low heat temperature solid state reaction according to claim 1 prepares rear-earth-doped calcium stannate fluorescent material, special Sign is：The after baking time is 60~120min.

9. preparing rear-earth-doped calcium stannate phosphor according to 1,2,5~8 any one of them low heat temperature solid state reaction of claim The method of material, it is characterised in that：The granularity 100% of the ball mill grinding to mixed material is less than 0.045mm.