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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An electron microprobe study of luminescence centers in cassiterite

Hall, Monte Ross January 1968 (has links)
An electron microprobe equipped with a device for making luminescence measurements has been used to determine the concentration of luminescence activators in zoned cassiterites of hydrothermal origin. Micron-scale growth zones contain variable amounts of Ti, Fe, W and other impurities. The impurity ions replace Sn⁴⁺ to produce luminescence centers. The relative intensity of cathodoluminescence and the amount and kind of impurity activators were simultaneously measured while scanning the growth zones with a micro-focussed electron beam. Two distinct emission bands were observed, a yellow-green (λ ~ 565 mµ) band for Ti-activation and a blue (λ ~ 440 mµ) band for W-activation. Measurements made on a heated sample show strong thermal quenching of the Ti-activated cathodoluminescence. The decay time for the Ti-activated emission, which is independent of temperature from 21°c to 275°C, is 0.168 msec. The cathodoluminescence spectrum for W-activation closely resembles that of self-activated CaWO₄ (Leverenz, 1946) although a higher oxygen coordination (VI) for W in cassiterite is to be expected, Fe occurring with Ti appears to enhance the Ti-activated emission. Fe occurring with W or Si quenches luminescence. / Master of Science

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