Thermal vacancy formation and <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>D</mi><mn>0</mn><mn></mn></mrow><mrow><mn>3</mn></mrow></msub></mrow></math></span> ordering in nanocrystalline intermetallic <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>(</mo><mrow><msub><mrow><mi mathvariant="normal">Fe</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow><mi mathvariant="normal">Si</mi><mrow><msub><mrow><mo>)</mo></mrow><mrow><mn>95</mn></mrow></msub></mrow><mrow><msub><mrow><mi mathvariant="normal">Nb</mi></mrow><mrow><mn>5</mn></mrow></msub></mrow></math></span>

L. Pasquini; A. A. Rempel; R. Würschum; K. Reimann; M. A. Müller; B. Fultz; H.-E. Schaefer

doi:10.1103/PhysRevB.63.134114

Thermal vacancy formation and ${D 0}_{3}$ ordering in nanocrystalline intermetallic $({Fe}_{3} Si)_{95} {Nb}_{5}$

L. Pasquini, A. A. Rempel, R. Würschum, K. Reimann, M. A. Müller, B. Fultz, and H.-E. Schaefer

Phys. Rev. B 63, 134114 – Published 15 March 2001

Abstract

The correlation between thermal vacancy characteristics and ${D 0}_{3}$ ordering in ball-milled nanocrystalline $({Fe}_{3} Si)_{95} {Nb}_{5}$ was studied by combined measurements of x-ray diffraction and positron annihilation. Structural stabilization due to grain boundary segregation of Nb enables high-temperature positron lifetime measurements up to 1023 K from which vacancy formation parameters identical to those in single-crystalline ${D 0}_{3} {Fe}_{3} Si$ are deduced. Measurements of coincidence Doppler broadening show that prior to the onset of thermal defect formation in the nanocrystallites, positrons are annihilated in Nb-enriched grain boundaries. The ${D 0}_{3}$ ordering of the initially disordered ${Fe}_{3} Si$ nanocrystallites is discussed on the basis of the thermal vacancy characteristics and self-diffusion behavior.

Received 22 September 2000

DOI:https://doi.org/10.1103/PhysRevB.63.134114

Authors & Affiliations

L. Pasquini^*

Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

A. A. Rempel

Institute of Solid State Chemistry, Russian Academy of Sciences, Pervomaiskaya 91, GSP-145, Ekaterinburg 620219, Russia
Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

R. Würschum

Institut für Technische Physik, Technische Universität Graz, Petersgasse 16, A-8010 Graz, Austria
Forschungszentrum Karlsruhe, Institut für Nanotechnologie, Postfach 3640, 76021 Karlsruhe, Germany

K. Reimann and M. A. Müller

Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

B. Fultz

Division of Engineering and Applied Science, 138-78, California Institute of Technology, Pasadena, California 91125

H.-E. Schaefer

Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

^*Corresponding author. Permanent address: Dipartimento di Fisica, Università di Bologna and Istituto Nazionale per la Fisica della Materia, viale Berti-Pichat 6/2, 40127 Bologna, Italy. E-mail address: pasquini@df.unibo.it

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Vol. 63, Iss. 13 — 1 April 2001

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