Lattice rare earth aluminates

In high radiation fields, the spinel crystal structure has been shown to change. The structure, while still cubic, becomes disordered with a reduction in lattice parameter. The disordered rock-salt structure has a smaller unit cell reflecting the more random occupation of the octahedral sites by both trivalent and divalent ions. Increased radiation damage results in the formation of completely amorphous spinels. Radial distribution functions (g(r)) of these amorphous phases have Al-0 and Mg-O radial distances that are different from equivalent crystalline phases. The Al-0 distance in the amorphous form is reduced from Al-O of 0.194nm in the crystalline phase to 0.18nm in the amorphous phase, while the Mg-O distance is increased (0.19nm in the crystal to 0.21 nm in the amorphous phase). Differences between the Al-O distances of crystalline and amorphous phases are a characteristic of both calcium and rare earth aluminates. 

We previously proposed an interpretation of thermal stabilization of supported catalysts by rare-earth elements [10, 11, 18] by means of interfacial structural coherence between alumina and rare-earth aluminates. This model, developped for lanthanum and neodymium, can be easily extended to cerium since LaAlOs, NdAlOs and CeAlOs are iso-structural mixed oxides with identical lattice parameters (a = 7.6 A). 

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