Copper-Activated Calcium Orthophosphate and Related Phosphors

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.

Section: Discussionmentioning

confidence: 79%

“…Emission and rej2ection spectra.--The spectral distribution of fluorescence under excitation by 3650A and that of reflection were measured at room temperature by the same method as reported in a previous paper (2).…”

Section: Reduction Of Phosphors--a Small Amount Of Thementioning

confidence: 99%

Luminescent Properties of Silver-Activated Magnesium Borate Phosphors

Uehara¹,

Kobuke²,

Masuda³

1960

“…Cu-activated fi-calcium orthophosphate and related phosphors.--Data for Cu-activated ~-calcium, fl-calcium.magnesium, and fl-calcium.zinc orthophosphate, together with those for pure orthophosphates without activators (used for the measurements) are shown in Fig. 5 and 6; the phosphors were prepared as reported in a previous paper (12).…”

Section: Preparation Of Phosphors and Experimental Resultsmentioning

confidence: 99%

“…For the measurement of the spectral qnergy distribution of fluorescence, a Zeiss Three Glass Prism Spectrometer combined with a photomultiplier (RCA 1P22) was used, as reported in a previous paper (12). All of the experiments mentioned above were made at room temperature.…”

Section: Mnmentioning

confidence: 99%

Wave-Length Dependence of the Quantum Efficiency and Absorption of Powder Phosphors

Uehara

Masuda

Kobuke

1960

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.

“…In order to remain on the 2:1 --2: 1:1 join or to arrive at the 2: 1:1 compound, it is necessary to compensate for the additional BaO with P~Os. The use of SrF2, as claimed in a recent patent by Uehara, Kobuke, and Tomishima (11), probably requires similar treatment, since it is likely that small amounts of Sr will substitute for Ba in the phosphor matrix.…”

Section: E~ect Of Phosphor Composition On Brightness-mentioning

confidence: 99%

The System BaO-TiO[sub 2]-P[sub 2]O[sub 5]: Phase Relations, Fluorescence, and Phosphor Preparation

Harrison¹

1960

The subsolidus phase relations were determined in the system normalBaO‐TiO2‐P2O5 by using x‐ray and petrographic techniques. Four compounds were isolated and individually prepared: 2normalBaO:TiO2:P2O5 melts congruently at 1197°±3°C ; normalBaO:TiO2:P2O5 has a rapidly reversible dimorphic inversion at 967°±5°C and it melts congruently at 1428°±3°C ; 4normalBaO:3TiO2:P2O5 melts incongruently at 1302°±3°C ; and normalBaO:4TiO2:3P2O5 melts incongruently at 1368°±3°C . The only compound in the system which is of the self‐activated type is 2normalBaO:TiO2:P2O5 . It has an emission similar to that of MgWO4 . Compositions of maximum fluorescence are restricted to the join 2normalBaO:P2O5‐2normalBaO:TiO2:P2O5 since compositions off this join contain either normalBaO:TiO2:P2O5 , 4normalBaO:3TiO2:P2O5 or TiO2 which have high u.v. absorption but are nonfluorescent phases.