The preparation and properties of copper-activated calcium orthophosphate and related phosphors are described. Copper-activated /~-calcium orthophosphate phosphor fired in a reducing atmosphere produces a strong blue fluorescence peaked at 4800A under excitation by 2537A and cathode rays. With
A number of powder phosphors have been measured by a direct optical method. Results are compared with other published values. Although slight discrepancies are found for magnesium and calcium tungstate at the 2537A position, the maximum quantum efficiency for magnesium tungstate is in good agreement with the published values. Good agreement is also found for impurity-activated phosphors. New data are presented for a number of orthophosphates. The quantum efficiency curves decrease more rapidly than the absorption curves toward both longer and shorter wave lengths from the peak position. The peaks of the quantum efficiency curves lie at longer wave lengths than those of the absorption curves. Reasons for these differences are discussed.Knowledge of the wave-length dependence of the quantum efficiency and absorption of phosphors provides an important foundation for the theoretical interpretation of luminescent properties, as well as for the development or technical application of phosphors.The quantum efficiency of powder phosphors has been measured by several methods (1), i.e., by direct optical, lamp efficiency calculation, calorimetric, and comparison methods. The second method used by Thayers and Barnes (2) and others (3-6) consists of comparing the measured luminous efficiency of a fluorescent lamp with its calculated maximum efficiency. This method involves some ambiguous assumptions concerning the optical characteristics of the phosphor layer in the fluorescent lamp. With the third or calorimetric method (1, 7) it is difficult to carry out the measurement over a wide range of exciting wave lengths, because an intense source of ultraviolet radiation is required but not available. The comparison method (1,6,8) is unsuitable to determine the absolute value of the quantum efficiency. In the present investigation, therefore, the first or direct optical method (9-11) was used to measure the wave-length dependence of many powder phosphors.
The preparation and properties of (Pb+Mn) ‐activated calcium cadmium silicate phosphors with various mole ratios of Cd to Ca are described. All phosphors produce a main, broad and variable emission band in the orange, and three minor, narrow and invariant bands at about 6880, 6950, and 7050Aå. The phosphors show a complicated shift of the main emission band with increasing Cd content, despite a linear relationship between Cd content and lattice spacings. The introduction of sulfate ions into the phosphor base changes the emission characteristics. With half of the Ca introduced as sulfate, the peak emission shifts from 6100, to 6200Aå. The results are discussed in the light of several assumptions.
Silver-activated magnesium borate phosphors are extremely sensitive to reducing agents in the presence of water or moist air. With progressive reduction, the color of fluorescence turns from bluish white to green, yellow, orange, and red under excitation by 3650A. At the same time the color of the phosphor powders changes from white to gray or black. Similar properties were found in some other crystals containing Ag. The characteristics of these phosphors show some similarities with photographic materials.
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