Kinetics of Quenched‐in Vacancies in Pure Platinum

Abstract

The kinetics of the annealing of vacancies in pure platinum quenched in water is investigated. S-shaped isothermal annealing curves are observed. After an initial transient region the annealing kinetics is approximately second order. Experimental results are discussed by assuming thermal equilibrium to exist between single-vacancies and di-vacancies. By using the deviations from purely second order kinetics, and comparing the calculated and measured values of the effective migration energy, estimates are made of the binding energy of a di-vacancy B, = (0.18 f 0.05) eV and the difference between the migration energy of single and di-vacancies d = (0.34 f 0.05) eV in platinum.Es wird die Kinetik des Ausheilens von Leerstellen von in Wasser abgeschrecktem reinem Platin untersucht. Isothermische Ausheilkurven mit charakteristischer S-Form werden beobachtet. Nach einem anfiinglichen tfbergangsbereich ist die Ausheilkinetik niiherungsweise von zweiter Ordnung. Die experimentellen Ergebnisse werden mit der Annahme eines gegenseitigen thermischen Gleichgewichts zwischen Einfach-und Doppelleerstellen diskutie& Aus den Abweichungen von der quadratischen Reaktionskinetik und aus dem Vergleich der berechneten und gemessenen effektiven Wanderungsenergien wird die Bindungsenergie einer Doppelleerstelle zu B, = (0,18 f 0,05) eV und die Differenz der Wanderungsenergien von Einfach-und Doppelleerstellen zu A = (0,34 f 0,05) eV abgeschatzt.

Vacancies, divacancies, and self‐diffusion in platinum

“…Our recovery measurements after quenching from temperatures near the melting point agree with those of Pol&k [6] in that processes with different activation energies contribute to the one broad annealing stage. Further agreement exists with regard to the observed annealing kinetics (nearly second order), an effective activation energy of NN 1 .O eV a t high vacancy concentrations, and an increase of EefP with decreasing concentration.…”

“…On theoretical grounds, we expect Eif -E,B < E f < ET. From the present experiments, the discussion of Section 4.2, and also from PolBk's [6] experiments (see below), we conclude that Eeff = 1.0 eV and Eeff = 1. 38 eV are two such distinguished values, following each other in this sequence with falling vacancy concentration.…”

“…This sudden transition is borne out by our own data ( Fig. 4 and 5) and also by those of PolAk [6]. I n his Fig.…”

“…Pol& [6] proposes the same value for EF as Jackson, but uses a chain of arguments whichin our opinionare subject to such uncertainties that the agreement with Jackson's value appears coincidental. I n his arguments Pol&k employs EY = 1.45 eV, which appears neither to be compatible with the analysis of the self-diffusion data (Section 6) nor with his own measurements of effective migration energies (which are in reasonable agreement with our own result and which support thus the assignment of Section 4.2).…”

“…3)It is advantageous to concentrate on the "distinguished" values of the apparent migration energies, since within fairly wide limits of the parameters involved their interpretation is not affected by the uncertainties in the choice of elv and of frequency and entropyfactors, in contrast to the attempts [6,7] to fit the concentration dependences of the annealing rate and the effective activation energies to theoretical expressions. energy over a wide concentration range is understandable.…”