Summarize fluorescent powder and its classification

Fluorescent powder (commonly known as luminous powder) is generally divided into luminous powder with light induced energy storage and luminous powder with radioactivity. Photoluminescent energy storage phosphor is a phosphor that stores light energy after being exposed to natural light, sunlight, ultraviolet light, etc., and then slowly releases it in the form of fluorescence after stopping light exposure. Therefore, it can still be seen at night or in dark places, lasting for several hours to more than ten hours. The luminescent powder with radioactivity is a kind of phosphor that is doped with radioactive substances, and the phosphor is excited to emit light by the continuous radiation of radioactive substances. This kind of luminescent powder emits light for a long time, but it is used cautiously because of its toxicity, harm and environmental pollution.
There are three main types of fluorescent powder for lamps. The first category is used for ordinary fluorescent lamps and low-pressure mercury lamps, the second category is used for high-pressure mercury lamps and self ballasted fluorescent lamps, and the third category is used for ultraviolet light sources, etc. There are also many kinds of phosphors, and the prices are different. The phosphors have the characteristics of good thermal stability, safety and environmental protection. They are suitable for all kinds of white light, and can adjust different colors such as red, blue, yellow, etc.
Fluorescent powder for fluorescent lamp and low-pressure mercury lamp
Calcium halide phosphate phosphor and rare earth tricolor phosphor activated by antimony and manganese.
Antimony and manganese activated calcium halide phosphate phosphor is a phosphor made by mixing a small amount of activators antimony (Sb) and manganese (Mn) into the fluorochlor apatite matrix 3Ca3 (PO4) 2 · Ca (F, Cl) 2, usually expressed as:
3Ca3(PO4)2·Ca(F,Cl)2:Sb,Mn
The raw materials used in many preparation methods of this phosphor can also be different, but the requirements for the purity of raw materials are high. When preparing the mixture, the amount of each raw material shall be calculated theoretically from the structure of apatite. In the halogenated calcium phosphate, the mole ratio of the sum of the mole atomic numbers of calcium and manganese to the mole atomic number of phosphorus in the phosphate radical is 4.9:3; Then it is weighed, mixed, milled, sieved, and sintered at a constant temperature of 1150 ° C for several hours in a certain atmosphere (usually nitrogen); After taking it out and cooling, it is selected under the ultraviolet lamp, and then grinded and sieved to be the finished product.
When the activator Sb absorbs the excitation energy, part of the energy will be released in the form of light radiation. Using the above phenomenon, as long as the content of Mn is changed, halogenated calcium phosphate phosphors with different color temperatures can be obtained.
The ability of phosphor to absorb radiation is related to the dispersion degree of phosphor, so the particle size of phosphor has a great influence on the luminous brightness. The particle size of the halogenated calcium phosphate phosphor depends on the particle size of the raw material CaHPO4. Therefore, the particle size of the phosphor can be controlled to a certain size (5~10µ) by obtaining a crystal CaHPO4 with a certain size and lattice, Thus obtaining high luminous brightness.
Among the rare earth tricolor phosphors, the red powder is europium activated yttrium oxide (Y2O3: Eu), the green powder is cerium and terbium activated aluminate (MgAl11O19: Ce, Tb), and the blue powder is low-priced europium activated barium magnesium aluminate (BaMg2Al16O27: Eu). Different color temperatures (2700-6500K) can be obtained by mixing the three powders in a certain proportion. The luminous efficiency of the corresponding lamp can reach 80-100lm/W, and the color rendering index is 85-90. In general, the higher the green powder content and the lower the blue powder content, the higher the luminous efficiency of the lamp. In addition, the color temperature increased with the increase of blue and pink; Red powder increases and color temperature decreases.
The matrix and activators of the three basic color powders are different, but the key of luminescence lies in the rare earth activators (europium, cerium, terbium, etc.), which use the transition of the outer rare earth metal ions (D → F) to emit light.
The tricolor fluorescent lamp using rare earth tricolor phosphors has many outstanding advantages. However, the high price of rare earth materials causes the high cost of tricolor lamps, which limits the development of tricolor lamps. Reducing the pipe diameter or using new coating technology to reduce the amount of tri color powder, and replacing one or two rare earth tri color powders with cheap other color powders, can also produce fluorescent lamps with high luminous efficiency and high color rendering, but the light attenuation may be larger.
Halogen calcium phosphate phosphor
Luminescence of halogenated calcium phosphate phosphor is activated by antimony (Sb) and manganese Mn. The activator atom occupies the position of calcium atom in the lattice. This material has a sensitization phenomenon: when the activator Sb absorbs the excitation energy, part of the energy is released in the form of optical radiation, and the other part is transferred to Mn in the process of so-called resonance transfer, so that Mn generates its own radiation. Therefore, the total radiation depends on the characteristics of the two activators, and changes with its proportion, and also depends on the proportion of fluorine and chlorine. If the manganese content is increased in Sb activated calcium halide phosphate, the orange yellow radiation will be increased, and the blue radiation will be reduced accordingly. Using the above phenomenon, as long as the content of Mn is changed, halogenated calcium phosphate phosphors with different color temperatures can be obtained.
Fluorescent powder for high pressure mercury lamp
The spectral distribution of high pressure mercury lamp is significantly different from that of low pressure mercury lamp (fluorescent lamp). In order to improve the efficiency of the lamp and the light color, the high-pressure mercury lamp is coated with phosphor inside the glass shell outside the discharge tube to convert 365 nm ultraviolet light, one of the main radiation wavelengths, into visible light. In the early period of high pressure mercury lamp, manganese activated magnesium fluogermanate or tin activated strontium zinc phosphate powder was used. Later, the phosphor YVO4: Eu used for color TV was used, its peak value was 619nm, and the corresponding lamp had high total luminous flux and good color rendering performance. Y (PV) O4: Eu phosphor has been developed, which is more suitable for the requirements of high-pressure mercury lamp.
Fluorescent powder for ultraviolet light source
It is a phosphor that can generate another longer wavelength ultraviolet light under the excitation of 253.7 nm or other shorter wavelength ultraviolet light. It has many kinds. (BaSi2O3): Pb phosphor is an effective ultraviolet phosphor with a peak value of 350nm. It is used as a black light lamp to trap and kill pests. Calcium orthophosphate [(Ca, Zn) 3 (PO4) 2: Tl] phosphor is an efficient powder for manufacturing health line lamps. Its emission wavelength is 280 ～ 350nm, and its peak value is 310nm. The copy lamp must have a spectral line matching the absorbance of the used photoreceptor or photoelectric surface. Therefore, the diazo copy lamp uses strontium pyrophosphate (Sr2P2O7: Eu), the electrostatic copy lamp uses magnesium gallic acid (MgGa2O4: Mn), zinc silicate (Zn2SiO4: Mn) and other ultraviolet phosphors.