Lamp phosphor

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... 

Plasma displays are based on the use of lamp phosphors which have been investigated for over 60 years. Optimization for plasma display panels (PDPs) has only taken place in the last few years and there is much room for improvement. 

The general properties of luminescent materials have been discussed in several texts.8,74,80,81 The most important lamp phosphors are listed in Table 2, together with their precursors used and some uses. Full synthetic details of most phosphors can be found elsewhere8,74 but an outline of traditional and newer methods is given below. 

Several classes of potentially useful fluorescent materials exist. Most lamp phosphors and many solid state materials are insulating compounds containing ionic activators. The spectra of the rare-earth activators resemble, to a first approximation,... 

The choice of sensor material determines range, sensitivity, and stability. By considering the latter factors, it is found that inorganic insulating compounds, such as most lamp phosphors and many solid state laser materials, are the most suitable materials for thermometric applications. Indeed, these materials are most commonly used in the existing commercial fluorescence thermometer schemes. 

This two-point measurement technique is used in the system reported by Wicker-sheim and Sun,(27) where a lamp phosphor, tetravalent manganese-activated magnesium fluorogermanate, mentioned above, is used as fluorescent sensor. The excitation... 

In summary, lamplight illuminates human activities, so lamp phosphors should feed their light into the human visual system with high visual efficiency. Rare-earth-activated phosphors tend to produce narrow, strongly saturated, brilliantly colored lights. 

K. H. Butler Fluorescent Lamp Phosphors. The Pennsylvania State University Press, London 980. 

Since oxide materials are extensively used in practical devices such as lamp phosphors or laser materials, their behavior at the nanoscale level has also been investigated. The size of yttrium oxide nanoparticles Y2C>3 Ln can be finely tuned by glycine-nitrate combustion synthesis. The overall equation of the exothermic reaction can be expressed as ... 

Reduction processes are frequently involved in doping of materials prepared for specific applications. Bai <5Sr(5MgF4 (< < 0.55) was doped with Sm2+ by addition of Sm metal to the charge for crystal growth [48], Eu2+ is the key ion in fluorescent lamp phosphors for emission of blue light. Respective reduction of Eu3+ is frequently achieved in H2 atmosphere, but in alkaline earth fluoride phosphates, Sn2+ may act as reducing agent [49]. 

Device Cathode-ray tube Plasma display panel Fluorescent lamp Phosphor-converted LED lamp... 

Srivastava AM, Sommerer TJ. Fluorescent lamp phosphors. Electrochem Soc Interface 1998 28-31. 

Butler, K. H. Fluorescent Lamp Phosphors, Technology and Theory, Philadelphia, Pennsylvania State University Press 1980... 

Since we intend to use this phosphor in a fluorescent lamp, we need to control its ultimate ultraviolet absorption properties. It is axiomatic that lamp phosphors must not contain an excess of a UV-absorbing constituent. In our case, this is SnOa. We thus add an excess of MgO. However, the magnesium compound only produces about 45 gm of MgO per 100 gm. of the hydroxy-carbonate. That is, it has an "assay" of 44.6%. The above formulation thus needs to be adjusted to compensate for this factor. Additionally, we would normally assay all of the other components as well. This is done by firing them to obtain the requisite oxides which are actually the reacting components in the above reaction of 1.3.86. Note that in some cases, the assay reflects only the amount of adsorbed water,... 

Note that these mechanisms apply mostly to semi-conducting phosphors like ZnS Ag and the like. The plasmon soon decays (- 10 sec.) to an excited state electron in the conduction band. If ionization occurs, large numbers of secondary electrons appear in the conduction band. This accounts for the high cathode-ray efficiency of the sulfides in general. Most lamp phosphors are insulators and do not respond well to electron excitation. 

However, there is a very usefiil reason for determining the type of luminescence decay curve present. Confirming the presence of an exponential decay curve means that only one type of emitter is jn sent. If a logarithmic decay process is found, it usually means that more than one type of emitting center is present, or that two or more decay processes are operative. While this does not occur very often, it is useful to know if such is present. This phenomenon occurs more in cathode-ray phosphors than in lamp phosphors, i.e.- sulfides vs oxide- hosts. 

Typical lamp phosphors are shown in the following table ... 

It should be noted that all of the above phosphors were described in a companion book, "The Chemistry of Artificial Lighting Devices- Lamps, Phosphors and Cathode-Ray Tubes", published by Elsevier in 1993 (ISBN 0-444-81709-3). In this volume, the exact methods for manufacture of these phosphors were presented along with the exact formulas and materials required to do so. 

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