Abstract

Calcium silicate phosphors activated with varying amounts of manganese luminesce yellow to orange under cathode-ray excitation, but are not excited by ultraviolet λ2537. If a small amount of lead is added with the manganese, the resulting material responds to λ2537 to give the same color as that produced by cathode rays, and in addition to the visible luminescence, there is an ultraviolet band at λ3400. The spectral distribution in the visible is dependent upon manganese concentration and on temperature.

If lead alone is used as an activator, the product gives emission entirely in the ultraviolet. Three emission bands are evident at approximately 3000A, 3340A, and 3500A, any one of which may be predominant, depending upon the conditions of preparation. The excitation spectrum also varies widely, having several maxima between 2000A and 3000A. When the phosphor is excited by 2288A line from a low pressure cadmium arc, a fourth broad band appears in the emission, which peaks about 3850A and extends far enough to the longer wave-lengths to be easily observed visually.

X-ray analysis with a Philips Geiger counter spectrometer demonstrates that the emission band at 3000A is due to the α-metasilicate, the one at 3500A to the β-metasilicate, while the 3340A band is due to the β-orthosilicate. During the firing process the orthosilicate is formed first by the reaction between the calcium oxide and silica in equi-molar proportions, and it reacts thereafter with additional silica to form metasilicate.

© 1949 Optical Society of America

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