Phosphors for fluorescent lamps

Some time ago Ca5(P04)3(F,Cl) (Sb, Mn) (halophosphate CHP) was used in fluorescent lamps. Lamps based on CHP have moderate energy efficiency (75 lm/W) and CRI of 50-60. 

Rare earth phosphors based lamps have efficiency of 100 lm/W and CRI of 80. BaMgAl 10O17 doped with Eu2+ (BAM) is used as blue emitting phosphor in fluorescent lamps. Photons are absorbed by Eu2+ ions and causes 4f-5d transition. Emission from Eu2+ occurs. 

MODERN ASPECTS OF RARE EARTHS AND THEIR COMPLEXES 

Red emission in lamps is due to YtOvEu. Excitation involves charge transfer transition from O2- ions to Eu3+ and then emission occurs due to f-f transitions in Eu3+ ions. 

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Welker T. 1991. Recent development on phosphors for fluorescent lamps and cathode ray tubes, J. Lumin. 48 49-56. 

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. 

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. 

Cd5Cl(P04)3 Mn2+ CdNH4P04 2H20, Cd02, MnNH4P04 H20, CdCl2 Red-emitting phosphor used in white blends for fluorescent lamps... 

Use Solvent for lacquers and paints, extraction of penicillin, photographic film, leather polishes, nail polish, warning odor, flavoring agent, printing and finishing fabrics, solvent for phosphors in fluorescent lamps. 

As a final step, let us now return to phosphors and show the various types of fluorescent lamps manufactured in terms of emittance hues and tolerances. In the following diagram, given as 6.7.48 on the next page, we have plotted the Standard Specifications for fluorescent lamps, in terms of the chromaticity as defined by MacAdam ellipses. 

It is these which are in use in the Industry for quality control of phosphors and fluorescent lamps. The ellipses show the color tolerance for emittance of each of the lamp hues. Thus, they are actually the Minimum Perceptible Color Difference, for each of these lamp colors. 

The activated rare earth phosphate phosphors can be used in all applications developed for phosphors in fluorescent lamps, cathode-ray tubes. X-ray intensify-... 

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. 

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