Impurity segregation to the surfaces of corundum-structured oxides

Abstract

Atomistic computer simulation methods have been used to calculate iso-and alio-valent segregation energies in the corundum-structured oxides Al₂O₃ and Cr₂O₃. The results show that the assumption made in the Langmuir isotherm, i.e. that the heat of segregation is coverage-independent, is not generally valid and that segregation is often both coverage-dependent and highly surface specific. The heats of segregation for Ca at the basal and prism planes of Al₂O₃ and Y at low index, and Mg and Fe at basal plane of Cr₂O₃ are given. Comparison with available experimental data is given, showing good agreement for Ca on the prism plane of Al₂O₃.