Determination of the vacancy formation enthalpy in chromium by positron annihilation

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5785688

Loper, G D; Smedskjaer, L C; Chason, M K; Siegel, R W

Doppler broadening of the positron annihilation lineshape in 99.99 at. % pure chromium was measured over the temperature range 296 to 2049/sup 0/K. The chromium sample was encapsulated in sapphire owing to its high vapor pressure near melting. Saturation-like behavior of the lineshape was observed near the melting temperature (2130/sup 0/K). A two-state trapping model fit to the data yielded a vacancy formation enthalpy of 2.0 +- 0.2 eV. This result is discussed in relation to extant empirical relations for vacancy migration and self-diffusion in metals and to data from previous self-diffusion and annealing experiments in chromium. It is concluded that the observed vacancy ensemble is unlikely to be responsible for the measured self-diffusion behavior. The implications of the present results in terms of our understanding of mechanisms for self-diffusion in chromium and other refractory bcc metals are discussed.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5785688
• Report Number(s): CONF-850169-3; ON: DE85010286
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
CHROMIUM
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DOPPLER BROADENING
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ELEMENTS
ENTHALPY
FERMIONS
FORMATION HEAT
INTERACTIONS
LEPTONS
LINE BROADENING
METALS
PHYSICAL PROPERTIES
POINT DEFECTS
POSITRONS
REACTION HEAT
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
VACANCIES