Characterization of the interface molybdenum sealing foil / vitreous silica

Molybdenum sealing foils doped with 0.52 wt% TiO2 and 0.55 wt% Y-Ce-mixed oxide were analyzed with regard to the distribution of the doping elements by means of different surface - analytical techniques before and after sealing with vitreous silica. Good adherence between the Mo-sealing foil and the vitreous silica, which is a prerequisite for a long - term vacuum tight seal, is determined by good wettability, mechanical and chemical bonding. Three different lamp types with vitreous silica envelopes, which were produced applying different sealing parameters, were used for the examination. The Y2O3 - Ce2O3 particles with diameters of 1 - 3 μm have the tendency to give an improved mechanical and chemical bonding, but only locally. TiO2 leads to the formation of a thin film on the nanometer scale on the metal substrate and to an improved adherence at the interface molybdenum / vitreous silica. It is concluded that the lateral distribution of the metal oxide between the molybdenum ribbon and the vitreous silica is significant for the long-term performance of the seal. (author)