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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 36, Iss. 7 — Jul. 1, 1946
  • pp: 372–381

On Infra-Red Sensitive Phosphors


JOSA, Vol. 36, Issue 7, pp. 372-381 (1946)

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FRANZ URBACH, DONALD PEARLMAN, and HENRY HEMMENDINGER, "On Infra-Red Sensitive Phosphors," J. Opt. Soc. Am. 36, 372-381 (1946)

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  1. The major part of the work reported here was carried out at the Institute of Optics of the University of Rochester under contract OEMsr-81 with the Office of Scientific Research and Development.
  2. Presented in part at the Winter Meeting of the Optical Society of America, March 7–9, 1946, Cleveland, Ohio.
  3. Acknowledgments: The work to be reported in this and some subsequent papers has extended over several years and many persons participated in it. Mr. Josef Kunz of Vienna deserves much credit for early recognition of some of its technical potentialities and for his support in the initial, sometimes trying, stages. Dr. Victor Demant did a major share of the chemical work in Vienna. In Rochester, Mr. Pliny E. Goddard, Mrs. Annie Urbach, Mrs. Myra Schwartz, Mr. Nelson R. Nail, and Mr. Carl Claus contributed much to the progress of our work. We are greatly indebted to Dr. Brian O'Brien for his constant support and encouragement throughout the work, and to various members of the NDRC for their help in overcoming initial difficulties. Our thanks are also due the many members of the laboratories which joined the infra-red phosphor work in 1943 (see previous paper) who gave us the benefit of their advice in numerous stimulating discussions.
  4. Present address: Research Laboratories, Eastman Kodak Company, Rochester, New York.
  5. Present address: General Aniline and Film Corporation, Easton, Pennsylvania.
  6. F. Urbach, Sitz. Akad. Wiss. Wien, Math. Naturwiss. 135, 163 (1926).
  7. P. Lenard, Handbuch der Experimental Pysik, Vol. 23. According to Lenard, stimulation is produced by "local heating" of the excited centers absorbing the stimulating radiation. They convert it into heat which remains localized due to a fantastic thermal insulation of the centers. The arguments for such an interpretation are remarkably plausible but, nevertheless, insufficient.
  8. An experienced worker in phosphor preparation, H. W. Leverenz, likened Lenard's recipes to matches: "They work but once." The difficulty of reproducing certain Lenard phosphors, together with Lenard's great authority and his emphatic claims of infallibility, sometimes lead to queer consequences, even to minor frauds. A well-known German firm sold a number of excellent phosphors certified by Lenard to be in accordance with his prescriptions. We did not succeed in reproducing one of these phosphors, a strontium sulfide-zinc preparation, in spite of great effort. According to Lenard it should have a very interesting infra-red sensitivity and the commercial sample showed some of it. Finally we found that the German sample was in fact a zinc sulfide-copper phosphor, the properties of which resemble very closely those ascribed by Lenard to the strontium sulfide-zinc phosphor.
  9. This was found by x-ray analysis.
  10. L. Levy and D. W. West, Trans. Faraday Soc. 35, 128 (1939); G. Urbain, Ann. de Chim. [8] 18, 350 (1909).
  11. S. Rothschild, Physik. Zeits. 37, 757 (1936).
  12. H. Froelich and G. R. Fonda, J. Phys. Chem. 46, 878 (1942).
  13. P. Lenard, Handbuchd er Experimental Physik, Vol. 23, pp. 30, 92.
  14. At low temperature quenching is apparently a much rarer occurrence than at room temperature, and stimulation is frequently obtained with the auxiliary activator alone. The same temperature dependence of efficiency which is observed for the process produced by absorption in the ground state seems to exist for the process produced by absorption in the excited state: fluorescence efficiency increases at low temperature.
  15. Apparently the quenching of the emission of the auxiliary activator is enhanced by small amounts of a dominant activator.
  16. If the spontaneous afterglow is very short, as with a pure europium phosphor, very small amounts of the auxiliary activator may produce an effect which is apparently opposite to poisoning: with the pure dominant activator, strong "fluorescence" but practically no afterglow is observed except by phosphoroscopic observation. The addition of a small amount of the auxiliary activator will increase the duration of the afterglow so as to make it conveniently observable.
  17. Professor G. P. Baxter of Harvard University provided us with some sulfides and phosphor blanks of extreme purity. These preparations seem to settle the question of whether "pure" strontium sulfide—containing fluxes, sulfate ion (probably oxide ion), but no activators—is luminescent (as is pure zinc sulfide). Strontium sulfide is not luminescent at room temperature. It is luminescent at the temperature of liquid air. There are indications that this residual low temperature luminescence still stems from traces of copper, although these are probably at most of the order of 10-2 parts per million.
  18. An extreme case of sensitivity to an impurity well worth recording occurred when the production of certain phosphor screens was transferred from our laboratory to a production plant. In order to insure immediate reproduction of our results our procedures were taken over without any change, using the identical materials and equipment even down to the silk bolting cloth through which the crushed phosphor powder was passed before the final "regeneration step." For some time we were puzzled by bright background spots which occurred only in the new production. These spots ruined most of the screens. It turned out that the bolting cloth obtained from the same manufacturer was marked with a different dye which obviously contained some copper. The special circumstances produced a very unusual sensitivity to this impurity. A quantity of 10-13 gram of copper sufficed to spoil a screen of one gram of material. (This corresponds to a few milligrams of impurities in the mass of a modern battleship.)
  19. The papers of W. Pauli [Ann. d. Physik 38, 870 (1912)] and F. Kittelmann [Ann. d. Physik 46, 177 (1915)], both of the Lenard school, form an interesting example. These papers are concerned with the preparation of selenide phosphors. Attempts to reproduce the preparations of both authors were met with scant success. From their papers and from our results it is quite obvious that they have missed some essential point in defining their conditions. We believe that Dr. Roland Ward and his collaborators (to be published) must be credited with the first description of a reproducible method of preparation of alkaline earth selenide and sulfoselenide phosphors.
  20. E. Tiede, Ber. 55, 69 (1922); A. Schleede and H. Gantzkow, Zeits. f. Physik. Chemie 106, 43 (1923).
  21. R. Ward, to be published.
  22. We are indebted to Dr. Herbert Friedman of the Naval Research Laboratories and to Dr. Bela Lengyel of the University of Rochester for their analyses of structure.
  23. As indicated before the europium-samarium-gadolinium phosphors led to the discovery of the activator interaction described. The gadolinium could be eliminated because its main effect was found to be caused by europium and samarium impurities contained even in the purest gadolinium preparation available to us. A specific effect of gadolinium seems to exist, but it is not significant. The europium emission obtained with our sulfide phosphors does not seem to be closely connected with europium fluorescence observed in pure europium salts, and in some europium activated compounds, such as calcium fluoride.
  24. B. O'Brien, J. Opt. Soc. Am. 36, 369 (1946).
  25. Cf. Fig. 2.
  26. Recently Dr. R. T. Ellickson has measured the light sum of the cerium-samarium type (abstract of the April, 1946 meeting of the American Physical Society at Cambridge, Massachusetts). He obtains light sums of about the same order of magnitude, but his results indicate that the number of quanta may be larger than the number of the samarium atoms and smaller than that of the cerium atoms, a result of considerable importance.

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