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

Abstract

Abstract. 2014 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 Al L2, 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.

Charge distribution in nano‐scale grains of magnesium aluminate spinel

“… Inversion parameters ( i ) of spinel samples, as measured by FTIR according to the methodology of Erukhimovitch et al., and as measured by ELNES in EELS, according to the methodology of Bruley et al . .…”

“…The inversion parameter was also calculated using the methodology of Bruley et al . The Al‐ L edge and the zero‐loss peak were measured simultaneously using the dual‐EELS method to verify the correct energy alignment of each spectrum.…”

“…Peak positions were determined by OPUS software using the second derivation method. The inversion parameter was calculated using the methodology of Erukhimovitch et al 42 The inversion parameter was also calculated using the methodology of Bruley et al 44 The Al-L edge and the zero-loss peak were measured simultaneously using the dual-EELS method to verify the correct energy alignment of each spectrum. Here, the collection semiangle was chosen as the smallest entrance aperture, 8.6 mrad, although this value is considerably larger than the optimal value of 0.6 mrad.…”

Electronic ionization induced atom migration in spinel MgAl2O4

“…However, previous work on the L 23 edges in MgAl 2 O 4 is scarce [17,18], although the O K edge has attracted considerable attention [19][20][21]. In our work, we used the full multiple scattering method with muffin-tin potentials (encoded in FEFF8 software) [22] to simulate the Mg and Al L 23 edges in a normal spinel, an inverse spinel, and a modified structure.…”

Scanning Transmission Electron Microscopy Analysis of Grain Boundaries in Creep‐Resistant Yttrium‐ and Lanthanum‐Doped Alumina Microstructures

“…The form of the Al-L 2,3 and the O-K energy-loss nearedge structures (ELNES) can yield insight on the local bonding and coordination of the aluminum and oxygen ions. [21][22][23][24][25][26][27] Figure 7 displays a spectrum-line series, consisting of 30 spectra of the Al-L 2,3 edge recorded along a line perpendicular to the grain boundary. Figure 8 shows the O-K edge series recorded across the same 30 nm long line.…”