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Investigates the chemical resistance properties of lead silicate glasses suitable for compression‐type glass‐to‐metal (GM) seals, to aggressive solvents, containing different amounts of Na, K, and Ba as modifier ions, in acidic and alkaline media. In general attack rate was observed to be higher in alkaline medium, with maximum dissolution of 53.35 mg/cm2 compared to the maximum of 10.6mg/cm2 in acidic medium after 50 hour exposure. An increase in the concentration of BaO was found to decrease the degradation rate, while samples with higher molar amounts of either Na2O or K2O showed more though similar damage rates. The degradation rate was observed to be linear for higher BaO concentration in alkali solution, whereas in other cases accelerated rates were observed with longer exposure time. GM seals prepared with glass, having higher BaO content, were less susceptible to damage and had higher insulation resistances.

The synthesis of lead silicate glass suitable for fabrication of compression type glass to metal seals has been studied with varying amounts of modifier ions (Na, K and Ba). A three-stage heating schedule was evolved for the preparation of glass. While, some of the constituents were taken in the form of oxides, the others were either in the form of carbonates or nitrates. Dependence of micro hardness of these glasses on the relative content of Na20, K20 and BaO was investigated. The concentration of these oxides was varied in the range 0-16 wt%. The modifier ions were seen to affect the micro hardness in a complex manner. While the micro hardness of glass without Na20 and 13 wt% K20 was found to be 504 kghnm 2, it turned out to be 547 kg/mm 2 for a glass with 13 wt% of Na20 in the absence of K20. However, the micro hardness of the glass synthesized having optimum composition with oxides of Na, K and Ba in the proportion of 5, 8 and 4 wt%, respectively was 455 kg/mm 2. The glass powder was found to be suitable for making single-and multi-pin seals which could withstand pressures up to 1-2x 104psi and vacuum of 10-8 Torr.

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Superconducting thin films of Y-Ba-Cu-0 have been prepared by SO Hz ac sputtering on polycrystalline SrTiO,, yttria-stabilized-Zr02, and MgO substrates. Films deposited on different substrate materials are required to be annealed at different temperatures to induce superconductivity. The optimum annealing temperature for a film depends on the reaction between the film and its substrate material. It appears that a correlation exists between the process of crystallisation and substrate-film reaction.