Micro hardness measurements on lead silicate glass

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 Na2O, K2O 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 Na2O and 13 wt% K2O was found to be 504 kg/mm(2), it turned out to be 547 kg/mm(2) for a glass with 13 wt% of Na2O in the absence of K2O. 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 1.2x10(4) psi and vacuum of 10(-8) Torr.