Reduction of Mercury Loss in Fluorescent Lamps Coated with Thin Metal-Oxide Films

The absorption of mercury into glass and metal-oxide coated glass tubes is investigated with the aid of Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), low-energy ion scattering, and thermal desorption mass spectroscopy. The absorption reaction of bare glass with activated mercury species is strongly reduced when the glass is covered with a thin oxide film. The concentration profile of the mercury measured in the films with the aid of RBS varied between a homogeneous distribution and a higher concentration of mercury close to the discharge side of the coating. XPS showed that the oxidation state of the mercury at the surface of the coatings was between that of metallic mercury and mercury(II) oxide. Thermal desorption mass spectroscopy showed that at least two different states of bound mercury were involved. The combination of the thermal desorption mass spectroscopy and XPS led to the conclusion that direct mercury-metal-oxide interactions contribute to the bonding of the mercury.