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All issues Volume 6 / No 1 (February 1995) Microsc. Microanal. Microstruct., 6 1 (1995) 1-18 Abstract
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Issue
Microsc. Microanal. Microstruct.
Volume 6, Number 1, February 1995
Page(s) 1 - 18
DOI https://doi.org/10.1051/mmm:1995103
Microsc. Microanal. Microstruct. 6, 1-18 (1995)
DOI: 10.1051/mmm:1995103

Spectrum-Line Profile Analysis of a Magnesium Aluminate Spinel Sapphire Interface

John Bruley, Ming-Wei Tseng et David B. Williams

Whitaker Laboratory 5 packes Av., Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pa 18017


Abstract
Spatially resolved chemical composition and spectroscopic line profiles have been gathered from the space charge region across a spinel/sapphire interface using a dedicated scanning transmission electron microscope. The electron energy-loss spectra reveal an excess of Mg (relative to stoichiometric spinel) along with Cr segregated to the interfacial zone. A quantitative least squares decomposition of a spectrum-line profile of the ${\rm Al\ }L_{{\rm 2,\ 3}}$ absorption edge fine structures into two standard components clearly highlights the transition from sapphire into spinel; further analysis indicates that the degree of site inversion, which is the fractional occupancy of tetrahedral sites by trivalent Al, increases within 5 nm of the boundary. The overall charge neutrality at the interface is maintained by the increased concentration of negative charge, probably interstitial O anions which are also present in excess quantity relative to stoichiometric spinel and sapphire.

PACS
8280P - Electron spectroscopy for chemical analysis photoelectron, Auger spectroscopy, etc..
7920K - Other electron surface impact phenomena.
6822 - Surface diffusion, segregation and interfacial compound formation.
6848 - Solid solid interfaces.

Key words
aluminium compounds -- electron energy loss spectra -- magnesium compounds -- sapphire -- scanning transmission electron microscopy -- space charge -- spectrochemical analysis -- surface segregation -- spinel sapphire interface -- spectroscopic line profiles -- space charge region -- scanning transmission electron microscope -- EELS -- excess Mg -- segregation -- Al L sub 2,3 absorption edge fine structures -- site inversion -- charge neutrality -- chemical composition -- MgOAl sub 2 O sub 3 Al sub 2 O sub 3


© EDP Sciences 1995