Prakt. Met. Sonderband 38 (2006) 235 
tin oxide revealed homogeneous distribution and a round as well as a needle-like morphology of 
ind oxide SnO, oxide particles (size about 300 to 500 nm) at 800°C (fig. 4). At 700°C we still 
e to both obtained uniformly distributed oxide particles but with much smaller size (about 100 nm) of 
ing ability the particles (fig. 5). So, lower temperature favors smaller particle size. Namely, with 
decreasing temperature increases the free energy change of oxide formation and 
decreases the rate of growth. Of course we know that the mean size of stable nuclei will 
be the smaller the greater the free energy change accompanying the formation of the new 
phase. At lower internal oxidation temperature (600°C) the mean particle size was even 
smaller than 100 nm (fig. 6a), but the oxides were preferentially distributed along the grain 
boundaries forming the inner oxide films (fig. 6b). Namely, the diffusion of oxygen is at 
lower oxidation temperature predominating along the grain boundaries. 
i ef 
J 
:800°C 
icles are Fig. 3: The EDX chemical mapping of precipitated SnO, oxide particles in internally 
] element oxidized Ag-Sn (2 at.% Sn) alloy, T=800°C, t=45min 
ture; and 
e able to 
a and 4b All microstructural changes during internal oxidation of alloys have also influence on its 
r the free electrical resistivity [10,11]. As a consequence of precipitation of oxide particles from the 
particles solid solution [12-14], the electrical resistivity of the silver — tin alloy strongly decreases 
side, the during the internal oxidation (fig. 7). The results of in-situ electrical resistance 
articles is measurements during internal oxidation of Ag-Sn (2 at.% Sn) alloy in air atmosphere (10° 
croscopy Pa) and at 800°C are presented in Fig. 7. The resistance curve, R(t), shows the electrical