Free Access
Microsc. Microanal. Microstruct.
Volume 6, Number 1, February 1995
Page(s) 1 - 18
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

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.

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