DIFFUSION OF Zr$sup 95$ IN BODY-CENTERED CUBIC IODIDE ZIRCONIUM

Chemically purifled Zr/sup 95/ was used in determining selfdiffusion coefficients in the body-centered cubic phase of iodide zirconium over the temperature range of 900 to 1750 deg C. In order to minimize effects of build-in of the daughter isotope Nb/sup 95/, all heat treatments were completed within 48 hr after the purification. The temperature dependence of the diffusion coefflcients could not be described by the usual Arrhenius-type equation. Instead, apparent values of the frequency factor D/sub o/ and the activation energy Q varied from 4.8 x 10/sup -6/ to 2.5 x 10/sup -2/ cm/sup 2//sec and 20700 to 46900 cal/mole, respectively, between the lower and upper extremities of the temperature range. Empirical treatment of the data indicated that Q is a linear function of temperature and that D/sub o/ varies with a power of the temperature. The data may be described in terms of the alpha to BETA transition temperature of 1136 deg K and the absolute temperature of the heat treatments by the following equation: D = 3 x 10/sup -6/ (T/1136)/sup 15.6/ exp (--19600 + 31(T -1136)/RT) cm/sup 2//sec. (auth