Single activated CaSiO3·normalMn phosphors absorb very little Λ 2537 radiation and, consequently, do not fluoresce appreciably when so excited. Under cathode ray excitation the emission is strong and is made up of two bands, one peaking at 5600 Å, the other at 6200 Å, the longer of the two becoming more prominent at higher concentrations of normalMnO . Complete solid solution of larger amounts of normalMnO is made possible by firing the phosphors in atmospheres of steam and of hydrogen. Single activated CaSiO3·normalPb phosphors produce blue or ultraviolet fluorescence, depending upon the conditions of preparation.Double activated CaSiO3·normalPb·normalMn phosphors, preferably prepared by steam firing, provide acceptable substitutes for ZnBeSilicate phosphors. They emit both visible light and useful ultraviolet when excited by X 2537. Their sensitivity, efficiency, and color make them useful for application in fluorescent lamps. They show exceptionally bright second stage phosphorescence, and remarkable temperature stability.In order to explain the mechanism of light production in double activated phosphors, internal optical excitation and paired Pb‐Mn centers are ruled out, and a mechanism first proposed by Rothschild is tentatively accepted.
Hexagonal, H2S‐normalfired ZnS:normalCu phosphors prepared with 0.05 to 1 per cent Cu are characterized by a yellow‐red luminescent emission obtained with ultraviolet, cathode ray, x‐ray, and electroluminescent excitation as well as with infrared stimulation. Peaked at 6500 Å, the emission is shown to consist of two bands, a strong red band at 6700 Å and a weaker yellow band at 5800 Å. The intensity of the yellow band declines toward zero at −196°C, while the red band increases in intensity and moves toward longer wave lengths. With electroluminescent excitation, the yellow‐red emission persists without changing to blue over the frequency range of 60 to 15000 cps.Washed with normalNaCN solution to remove excess free copper sulfide, the phosphors retain only a certain percentage of the amount of Cu originally added. The amount of retained Cu is one or two orders of magnitude larger than in conventional phosphors, indicating a limit of solubility near 0.3 per cent Cu. The incorporation of Cu into the normalZnS lattice must be explained without benefit of charge compensating ions. To account for the double band emission and the infrared stimulability, the presence of two species of Cu atoms may be assumed.
With increasing concentrations of Cu and A1 in H~S-fired Zn(A1)S: Cu phosphors, the emission spectrum is shifted from green to orange under 3650 A excitation. The emission of these triple sulfides consists of three sub-bands of such relative intensities that the presence of a single band is simulated. The bands have different temperature, decay, and excitation characteristics. Among other substituents, the elements Sc, Ce, Pr, and Nd are of interest, as they produce infrared stimulability even with high activator concentrations.
The question is .raised whether phosphors, and in particular the silicate phosphors used in fluorescent or F lamps, are subject to deterioration either before application or during normal burning of the lamps. It is shown that Zn-Be silicate phosphors usually contain a small amount of free Mn20 8, lodged at the crystal surface, and responsible for slight discolorations and lower than "normal" fluorescent bright-heSS. This brown oxide forms when the phosphors are exposed to air or oxidizing atmospheres in a range of surface instability between roughly 350 ~ and 1,000 ~ C, either during cooling from higher temperatures or upon reheating. In reducing atmospheres or in vacuo this process of chemical deterioration is reversible. The phosphors may be stabilized by removal of superficial manganese. This is accomplished, for example, with an acid SO2 solution. In order to measure the brightness of phosphors taken from finished or burned F lamps, the powders must be freed of mercury and its compounds (oxide, nitride). This is best done by vacuum distillation at low temperatures. Phosphors removed from many lamps were demercurized and found to be about as bright as phosphors removed from unburned lamps of the same manufacture. Occasional gains as well as losses, both of the order of 1% to 3%, are accounted for. Recovery of flfll brightness is taken as one proof that the phosphors do not further deteriorate during lamp life. Other tests were made with jacketed lamps, such as a quartz lamp inside a glass envelope bearing the phosphor, and a quartz-vycor :~791 combination inner tube in a glass lamp coated with a special phosphor. In the former experiment, the phosphor was exposed to excited mercury and to short ultraviolet (uv) radiation for 600 hr. During this time the lamp output declined 25%, but the recovered phosphor was 103% of the original in brightness. The quartz-vycor combination served to demonstrate a strong afterglow which is excited by X 1,849 radiation in the mercury arc. Photographic and photoelectric measurements of this afterglow, made on lamps of standard design, showed that the /, 1,849-stimulated phosphorescence of this special phosphor depreciates at the same rate during lamp life as the full h 1,849 + 2,537stimulated fluorescence, as measured by the lumen output of the lamps. t Manulcript received February 15, 1945. $ Lamp Development Laboratory, General Electric Co., Cleveland, Ohio. 429 unless CC License in place (see abstract). ) ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-04-04 to IP
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