skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The effects of cation–anion clustering on defect migration in MgAl 2O 4

Abstract

Magnesium aluminate spinel (MgAl 2O 4), like many other ceramic materials, offers a range of technological applications, from nuclear reactor materials to military body armor. For many of these applications, it is critical to understand both the formation and evolution of lattice defects throughout the lifetime of the material. We use the Speculatively Parallel Temperature Accelerated Dynamics (SpecTAD) method to investigate the effects of di-vacancy and di-interstitial formation on the mobility of the component defects. From long-time trajectories of the state-to-state dynamics, we characterize the migration pathways of defect clusters, and calculate their self-diffusion constants across a range of temperatures. We find that the clustering of Al and O vacancies drastically reduces the mobility of both defects, while the clustering of Mg and O vacancies completely immobilizes them. For interstitials, we find that the clustering of Mg and O defects greatly reduces O interstitial mobility, but has only a weak effect on Mg. Lastly, these findings illuminate important new details regarding defect kinetics relevant to the application of MgAl 2O 4 in extreme environments.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1329597
Report Number(s):
LA-UR-16-23859
Journal ID: ISSN 1463-9076; PPCPFQ
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 29; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; material science

Citation Formats

Zamora, Richard J., Voter, Arthur F., Perez, Danny, Perriot, Romain, and Uberuaga, Blas P. The effects of cation–anion clustering on defect migration in MgAl2O4. United States: N. p., 2016. Web. doi:10.1039/C6CP03931F.
Zamora, Richard J., Voter, Arthur F., Perez, Danny, Perriot, Romain, & Uberuaga, Blas P. The effects of cation–anion clustering on defect migration in MgAl2O4. United States. doi:10.1039/C6CP03931F.
Zamora, Richard J., Voter, Arthur F., Perez, Danny, Perriot, Romain, and Uberuaga, Blas P. 2016. "The effects of cation–anion clustering on defect migration in MgAl2O4". United States. doi:10.1039/C6CP03931F. https://www.osti.gov/servlets/purl/1329597.
@article{osti_1329597,
title = {The effects of cation–anion clustering on defect migration in MgAl2O4},
author = {Zamora, Richard J. and Voter, Arthur F. and Perez, Danny and Perriot, Romain and Uberuaga, Blas P.},
abstractNote = {Magnesium aluminate spinel (MgAl2O4), like many other ceramic materials, offers a range of technological applications, from nuclear reactor materials to military body armor. For many of these applications, it is critical to understand both the formation and evolution of lattice defects throughout the lifetime of the material. We use the Speculatively Parallel Temperature Accelerated Dynamics (SpecTAD) method to investigate the effects of di-vacancy and di-interstitial formation on the mobility of the component defects. From long-time trajectories of the state-to-state dynamics, we characterize the migration pathways of defect clusters, and calculate their self-diffusion constants across a range of temperatures. We find that the clustering of Al and O vacancies drastically reduces the mobility of both defects, while the clustering of Mg and O vacancies completely immobilizes them. For interstitials, we find that the clustering of Mg and O defects greatly reduces O interstitial mobility, but has only a weak effect on Mg. Lastly, these findings illuminate important new details regarding defect kinetics relevant to the application of MgAl2O4 in extreme environments.},
doi = {10.1039/C6CP03931F},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 29,
volume = 18,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share:
  • No abstract prepared.
  • Abstract not provided.
  • The effects of irradiation by F, P, and PF{sub 4} on optical properties of GaN were studied experimentally and by atomistic simulations. Additionally, the effect of Ag was studied by simulation. The irradiation energy was 0.6 keV/amu for all projectiles. The measured photoluminescence (PL) decay time was found to be decreasing faster when irradiation was done by molecular ion compared to light ion irradiation. The PL decay time change is connected with the types of defect produced by different projectiles. Simulation results show that the light ions mainly produce isolated point defects while molecular and heavy ions produce clusters of pointmore » defects. The total amount of defects produced by the PF{sub 4} projectile was found to be very close to the sum of all defects produced in five individual cascades started by one P and four F single ions. This and the similar depth profiles of damage produced by molecular and light ion irradiations suggest that the defect clusters are one of the important reasons for fast PL decay. Moreover, the simulations of irradiation by Ag ions, whose mass is close to the mass of the PF{sub 4} molecule, showed that the produced defects are clustering in even bigger conglomerates compared to PF{sub 4} case. The latter has a tendency to split in the pre-surface region, reducing on average the density of the collision cascade.« less
  • Building upon work in which we examined defect production and stability in spinels, we now turn to defect kinetics. Using temperature accelerated dynamics (TAD), we characterize the kinetics of defects in three spinel oxides: magnesium aluminate MgAl{sub 2}O{sub 4}, magnesium gallate MgGa{sub 2}O{sub 4}, and magnesium indate MgIn{sub 2}O{sub 4}. These materials have varying tendencies to disorder on the cation sublattices. In order to understand chemical composition effects, we first examine defect kinetics in perfectly ordered, or normal, spinels, focusing on point defects on each sublattice. We then examine the role that cation disorder has on defect mobility. Using TAD,more » we find that disorder creates local environments which strongly trap point defects, effectively reducing their mobility. We explore the consequences of this trapping via kinetic Monte Carlo (KMC) simulations on the oxygen vacancy (V{sub O}) in MgGa{sub 2}O{sub 4}, finding that V{sub O} mobility is directly related to the degree of inversion in the system.« less