Incorporation and migration of Cr~3+ and PO~3-_4 species in anodic alumina

摘要

Through the use of a thin layer covering an aluminium surface, obtained by electropolishing and subsequent dipping in a hot CrO_3-H_3PO_4 solution, as source for incorporation of Cr~3+ and PO~3-_4 species, the migrations of he respective species in growing anodic alumina have been examined successfully. It was found that the Cr~3+ species migrate outward and the PO~3-_4 species migrate inward. The rates of migration of Cr~3+ species relative to that of Al~3+ ions and PO~3-_4 ions relative to that of O~2- ions are 0.74 and 0.51, respectively.