Outgassing of CRT shadow mask coatings caused by electron bombardment

A UHV system with a quadrupole mass spectrometer in a nude condition was used to investigate the outgassing characteristics of the coatings of CRT shadow mask during electron bombardment. The coatings of Bi/sub 2/O/sub 3/, WO/sub 3/ and Fe/sub 3/O/sub 4/ were electron bombarded with energies from 15 to 30 keV and currents up to 100 mu A. The Bi/sub 2/O/sub 3/ coating released a larger amount of gas than WO/sub 3/ and Fe/sub 3/O/sub 4/, but its amount decreased to the same extent as that of the others with heat treatment at temperatures higher than 450 degrees C. The main components of released gas were CO, CO/sub 2/, CH/sub 4/, and H/sub 2/, and the release of O/sub 2/ was also observed for the Bi/sub 2/O/sub 3/ coating without heat treatment. This O/sub 2/ release was found to be caused by the decomposition of unstable carbonate, which was formed by the reaction of Bi/sub 2/O/sub 3/ with CO/sub 2/ in the presence of moisture during the preparation of the coating. These outgassing behaviors are discussed quantitatively from the viewpoint of preventing oxidizing gas release.<
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