Bulk diffusion of gold in single-crystal iridium

The method of secondary-ion mass spectrometry was used to measure coefficie nts of bulk diffusion of gold in a temperature range of 1300-2000 K (0.48-0 .75T(m)) in single-crystal iridium annealed in an ultrahigh vacuum. The par ameters of the Arrhenius plots of these diffusion coefficients were found t o be as follows: the enthalpy of activation Q = 423.2 +/- 4.6 kJ/mol and th e preexponential factor D-0 = (4.92 +/- 0.2) x 10(-5) m(2)/s. It Was shown, using the linear dependence of the enthalpy of activation of self-diffusio n Q(SD) of d transition metals on the universal homologous temperature V = 0.3T(m) + 0.7 theta, that the available parameters of bulk self-diffusion o f iridium [1] agree completely with the linear dependence Q(SD)(V) for the d transition metals and that the corrected value is (Q(SD))(Ir) = 449 kJ/mo l. The difference of the enthalpies of activation of the bulk diffusion of gold and of self-diffusion in iridium qualitatively agrees with the availab le charge dependences of such differences for the bulk diffusion of isocori c impurities in single crystals of tungsten and gold [2-8].