Nonstoichiometry in line compounds
- 502 Downloads
Phases having compositional fields narrower than about 1 at.% and appearing as lines in binary phase diagrams often are assumed to have properties independent of composition. That such an assumption can be seriously in error is illustrated by recent measurements on pairs of samples prepared to have compositions at opposing phase boundaries. Two microscopic properties, lattice locations of highly dilute solutes and diffusional jump frequencies, were studied, respectively, through measurement of static and dynamic nuclear quadrupole interactions using the method of perturbed angular correlation of gamma rays (PAC). At opposing boundary compositions, PAC probe atoms have been observed to occupy different lattice sites or to have jump frequencies differing by a factor of 100. Such gross differences suggest measurements of other properties of line compounds should be made on pairs of samples having the opposing boundary compositions in order to avoid inconsistent or unreproducible results.
KeywordsElectric Field Gradient Probe Atom Lattice Location Perturb Angular Correlation Perturbation Function
I thank Aurélie Favrot, Li Kang, Egbert Rein Nieuwenhuis, Denys Solodovnikov, Jipeng Wang and, especially, Matthew O. Zacate, who contributed significantly to the measurements and analysis. This work was supported in part by the National Science Foundation under Grants DMR 00-91681 and 05-04843 (Metals Program).
- 1.Massalski TB (ed) (1990) Binary alloy phase diagrams. ASM International, Materials Park, OHGoogle Scholar
- 2.Zacate MO, Collins GS (2004) Phys Rev B69:174202Google Scholar
- 3.Zacate MO, Collins GS (2004) Phys Rev B70:24202Google Scholar
- 4.Zacate MO, Favrot A, Collins SG (2004) Phys Rev Lett 92:225901; and Erratum, Phys Rev Lett 93:49903Google Scholar
- 5.Collins GS, Favrot A, Kang L, Solodovnikov D, Zacate MO (2005) Defect Diff Forum 237–240:195–200Google Scholar
- 7.Schatz G, Weidinger A (1996) Nuclear condensed matter physics. John Wiley, New YorkGoogle Scholar