Phosphor, fluorescent

Sunlamps A sunlamp is similar to a black lamp, except that a different type of phosphor is used and the lamp envelope transmits UV. Figure 16.5 shows a typical spectral distribution from a commercial sunlamp. The wavelength corresponding to maximum power is shifted to lower wavelengths (— 310 nm), compared to black lamps, and there is significant intensity down to 270 nm. However, the intensity decreases rapidly above 330 nm. The mercury lines can again be seen superimposed on the phosphor fluorescence. 

Some of the new lower wattage lamps may also be coated for safety purposes with clear plastic which may be absorptive and effect results. One of the problems with using bare fluorescent lamps is that they do not filter out all incident UV radiation used to make the phosphor fluoresce. These lamps are made with the... 

Use Pigments and inks, ceramic glazes, pyrotechnics, phosphors, fluorescent screens, scintillation counters, rectifiers, photoconductor in xerography, transistors, photovoltaic cells, solar cells, catalyst in photodecomposition of hydrogen sulfide. 

For a typical measurement, the phosphor transducer is mounted on the test surface, and a pulse laser is used to excite the transducer. Then, the time evolution of the phosphors fluorescence spectrum is captured by an optic filter and an optoelectronic device. The fluorescence thermometer should be carefully calibrated before application in temperature measurements. 

Uses Pigment in paints, printing inks, ceramic glazes, pyrotechnics, phosphors, fluorescent screens, scintillation counters, rectifiers photoconductor in xerography, transistors, photovoltaic cells, solar cells catalyst in photodecomposition of hydrogen sulfide Manuf./Distrib. ABCR http //www.abcr.de] Acres Org. http //www.acros.be] Barker Ind. http //www.barkerind.com] Noah http //www.noahtech.com... 

Phosphor Fluorescent coating used in night vision technology that emits green light when electrons strike the coating. 

Lanthanide luminescence apphcations have already reached industrial levels of consumption. Additionally, the strongly specific nature of the rare-earths energy emissions has also led to extensive work in several areas such as photostimulable phosphors, lasers (qv), dosimetry, and fluorescent immunoassay (qv) (33). 

Nonradiative Decay. To have technical importance, a luminescent material should have a high efficiency for conversion of the excitation to visible light. Photoluminescent phosphors for use in fluorescent lamps usually have a quantum efficiency of greater than 0.75. AH the exciting quanta would be reemitted as visible light if there were no nonradiative losses. 

In fluorescent lamps, phosphors are coated on the inside of the lamp tube using a slurry containing the powder and a Hquid which is either poured down through the tube, up-flushed, or in some cases the tubes are filled and then drained. Because of concerns over having volatile organic solvents in the air, the hquid medium containing the powder is usually water with an added agent, a thickener, to increase the viscosity of the suspension, such as poly(methacryhc... 

The Calcium Halophosphate Phosphors. Early fluorescent lamps used various combinations of naturally occurring fluorescent minerals. The development of the calcium halophosphate phosphor, Ca (P0 2(Cl, F) Sb ", Mn, in the 1940s was a significant breakthrough in fluorescent lighting (7). As is often the case in new phosphor discoveries, this phosphor was found accidentally while searching for phosphors for radar screens. 

Because it is stiU by far the most commonly used phosphor in fluorescent lamps, calcium halophosphate total production far exceeds that of all other phosphors put together, in excess of 1000 metric tons per year. 

The cost of rare-earth phosphors in fluorescent lamps is often reduced by double coating the lamps. The rare-earth phosphor blend is coated over a base layer of the inexpensive halophosphate phosphor (Fig. 9). In this configuration it absorbs a disproportionate amount of the uv discharge. For example, about 70% of the uv is absorbed in the inner coating with only one layer of triphosphor particles on the inside. 

Fig. 9. A modem fluorescent lamp coating including a conductive layer of Sn02 F, then a protective coating of finely divided alumina, followed by the inexpensive halophosphate phosphor, and finally a thin layer of the triphosphor rare-earth blend.

Luminescent Pigments. Luminescence is the abihty of matter to emit light after it absorbs energy (see Luminescent materials). Materials that have luminescent properties are known as phosphors, or luminescent pigments. If the light emission ceases shortly after the excitation source is removed (<10 s), the process is fluorescence. The process with longer decay times is referred to as phosphorescence. 

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