Tracer Impurity Diffusion in Liquid Metals: Period 5 Elements in Gallium

The diflusivities of 110A g and of 121Sn in liquid Ga have been measured and compared with recent data for 115Cd and 114In in Ga. The results can be reasonably well expressed by Arrhenius-type relations D = D0 exp{ — Q/R T}, with D0 = 2.2 x 10“ 4 cm2/s, @ = 1.68 kcal/mole for Ag, and D0= 1.6 x 10-4 , @ = 1.49 for Sn. A t temperatures above some 380 °K the diffusion coefficients of Ag, Cd and In in gallium are practically equal, while that of Sn lies about 10% lower. Even at the lowest temperatures the D-values of the different tracers vary by less than 10% from a mean. The low temperature points appear to fall somewhat below the best straight lines in the D vs T diagram. No obvious dependence on valency is discerned; the only reasonable systematics implied by the behaviour of the four elements of period 5 is the inverse root dependence on tracer mass. In a systematic investigation of tracer diffusion in liquid Ga, we have previously reported the results fo r 72G a 4, 198A u 2, 65Zn and 115C d 3, and 114I n 4. The same “ infinite capillary” technique has now been used to measure the diffusion coefficients of 110A g and 121Sn. The new data are listed in Table 1. In Fig. 1 the experimental points fo r A g and Sn are shown together with lines representing self-diffusion and the diffusion of the other two period 5 elements (i. e. Cd and In ) in Ga. In the diagram, earlier results fo r A g in Ga 5’ 6 are also shown (crosses), in obviously good agreement with the present series.