Effect of addition of palladium on properties of Ag₂Hg₃ (γ₁) phase

The effect of palladium addition on the microstructure, compressive strength, creep rate and mercury release rate of Ag₂Hg₃ (γ₁) phase was evaluated. Experimental results indicated that fairly pure γ₁ phase could be fabricated using the present trituration method. The heat treatment of γ₁ at 90°C increased porosity level, increased dimensional shrinkage, increased mercury vapour release and enhanced the formation of β₁ phase. Addition of palladium in γ₁ slowed down the amalgamation reaction, largely suppressed the phase transition to β₁ and caused a slight shift in open circuit potential toward the anodic direction. Although the overall anodic polarization profiles did not show a significant effect of palladium, scanning electron microscopy revealed morphological differences between pure and palladium-containing γ₁. Addition of palladium in γ₁ also increased compressive strength, increased creep resistance, and largely reduced both mercury vapour and ion release rates. Considering overall performance, the optimal palladium content in γ₁ seems to be in the range between 0.50 and 0.75 wt%.