Method for synthesis of long persistence materials

  1. High temperature solid phase reaction method

Long afterglow which was prepared by using high temperature solid instead should process is: according to the calculation of the mole ratio of says take spectrum pure co: A120, sr – and Eu203 raw material, and after a certain amount of canadians flux blending fine grinding, first by 1500 ℃ calcination 3 hours, then in the reduction of gas and 1200 ℃ 1400 ℃ roasting 2 one 4 hours, only made larger phosphor, hardness after crushed into small pieces, then ball mill to produce powdered aluminate inscription shop long residual material. Because the phosphor synthesized by high temperature solid phase reaction method requires a slow growth process of crystals in a high temperature state for several hours, the synthesized phosphor grains grow gradually and are relatively large. In addition, the hardness of synthetic phosphor is larger, the test shows that it is harder than glass, the hardness between 6 and 7. In order to make phosphor into powder long afterglow material, ball grinding process must be carried out. For this reason, the lump phosphor must be broken into a certain size first, and then the corundum ball machine with high hardness and price is used to grind into powder long afterglow material. Because the size of the ball grinding pot block size difference is large, in the ball grinding, is often the larger block just fine grinding, and the smaller block has been ground very fine, it may destroy the long afterglow material crystal shape, affect the luminance, or even make luminance greatly decreased. According to the measured comparison of BM – 3 luminance meter imported from Japan for the self-made mingpu aluminate phosphor, the luminance of the pulverized long afterglow material is only about a quarter of that of the lumpy phosphor. In addition to the above main reasons, there is also the problem of grinding and blending of raw materials. Since it is impossible to achieve a very uniform degree after grinding and blending by human or mechanical means and then using high temperature solid phase reaction method (dry method), the non-luminous points on the section of phosphor prepared by this method can be observed. The formation of these points is caused by the fact that the raw materials are not grinded and mixed. For this reason, the raw materials can be prepared into a solution according to a certain proportion, and the high temperature solid phase reaction method (wet method) can also be used to prepare long afterglow materials for dehydration. As long as the technology is reasonable, it can solve the problem of traditional artificial or ball mill mixing inhomogeneity.

  1. Sol-gel method

Sol-gel method is one of the methods to prepare materials. It is starting to replace the traditional high temperature solid phase reaction method to prepare inorganic materials. Sol-gel method started in the middle of the 19th century, but it was not until 1971 that German scholars successfully prepared multi-component glass by using so-gel method. Now it has been widely used in the preparation of ceramic materials and ultra-fine materials such as t6J, etc. In recent years, phosphor powder has also been gradually prepared by using 501 Gel method. The technology of sol-gel method is firstly to prepare metal soluble salt which is easy to be hydrolyzed, then it is gradually gelated in the process of hydrolysis and polycondensation in the aqueous solution of ethanol. In order to speed up the polycondensation reaction rate, catalysts should be added. Finally, the required materials are prepared after dehydration and dealcoholation, drying and sintering. CasiO prepared a sol gel method available: Mn2 +, Pb2 +, phosphor, raw materials for the analysis of pure Ca play (N03) 2, 4 O, Mn (CH3COO) 2 and pb (NO3) 2, as well as the spectrum of pure Si (OCH 3) 4, according to certain proportion soluble in ethanol aqueous solution, and heat preservation under 60 ℃ 3 a 4 hours, to strengthen the gel forming, remove water and alcohol and make the complex decomposition, finally in 1150 ℃ heat treatment 1 can be calcium silicate phosphor was 1.5 hours. Compared with the high temperature solid phase reaction method, the biggest advantages of sol-gel method in preparing phosphor powder are low synthesis temperature and highly uniform material composition, which can reach the average homogeneity at the molecular level. Therefore, the fluorescence material prepared by sol-gel method has better optical properties, and the required activator content can be reduced. For preparing long afterglow materials, the cost can be reduced and the market competitiveness can be strengthened. Because paving is a rare earth resource with low content, it has low output and high price. When preparing long aftershine materials by S01 Gel method, the paving content can be reduced and the cost can be significantly reduced.

  1. Combustion method

For powder preparation methods of fluorescent material in addition to the high temperature solid phase reaction method and sol gel method, still can use the burning process, fluorescent material is we have been successfully synthesized by using combustion silver shop store aluminate long afterglow material, this is at lower temperature (500 ℃ 700 ℃), fast under the condition of a 5 minutes (3 minutes) in the synthesis of phosphor will not, hardness is small, easy to shatter, small grain size, no significant luminescence brightness down after fine grinding. The process of preparing luminescent materials by combustion method is firstly to make the raw materials into nitrate, and then add a proper amount of urea or glycine and other reducing agents. After fully mixing and heating, when the reactants reach the ignition temperature of exothermic reaction, the combustion is maintained on its own after ignition, and the combustion products are the required fluorescence materials. The long afterglow material of silver aluminate was synthesized by combustion method. Raw materials for “fluorescent” EuZO3 and DyZO:, and “analytical pure grade” SrC03 and Al (NO3) 3, according to certain proportion to the front after nitrate solution made up of three compounds, mix the mole fraction of four kinds of raw materials in a specific, plus people play Bo3 and urea, after being all substances dissolved, directly move people has preheat to 600 ℃ in the muffle furnace. Gradually with the reducing of water, vessel solution presents a viscous state of sol, continue to heat, can be observed as oxidant nitrate and urea as reductant intense exothermic oxidation reduction reaction, escape of gas, and, in turn, burning, burning flame appear yellow red light, the combustion process can be completed in a few seconds, can obtain white “mushroom cloud” product.

Compared with the high temperature solid phase reaction method, the long afterglow material prepared by the combustion method is not only fast and energy saving, but also the pulverized long afterglow material prepared by the combustion method has higher brightness and longer afterglow time than that prepared by the high temperature solid phase reaction method. This is because the combustion is characterized by fast moving combustion crest, high spontaneous temperature (10000k-4000k), so the long afterglow material synthesized by the combustion method has small grain size, and the crystal shape is almost undamaged after being ground into powder. The luminance of the product is not significantly different from that of the white “mushroom cloud” shaped product under the same irradiation condition. This is the same as the product prepared by sol-gel method, with smaller crystallization. However, the grains prepared by high temperature solid phase reaction method are gradually grown, so the particles are coarser. In grinding or ball grinding,

It is often the larger block just fine, and the smaller block has been ground very fine. It is even possible to destroy the crystal shape, affect its luminous performance, so that the luminance is greatly reduced

Drop.

Compared with sol-gel method, fluorescence materials with small crystal size and excellent luminescence performance can be obtained by the combustion method. However, the whole process of sol-gel method for the preparation of calcium silicate phosphor takes 4-5.5 hours, which is much longer than the combustion method of 4-5 minutes. And sol gel method need to be done in more than 1000 degrees high temperature heat treatment, and burning method the muffle furnace temperature is only about 600 ℃, so low temperature combustion method process is a big advantage. Compared with high temperature solid phase reaction method and sol-gel method, combustion method has the advantages of time-saving and energy saving, and conforms to the energy saving requirements of green lighting materials. Therefore, combustion method is a promising new method for preparing luminous materials. In a word, whether the preparation technology and method is reasonable or not is the key to obtain good long afterglow materials. Therefore, efforts should be made to find a more reasonable preparation method, technology and formula.