Study by Extended X‐ray Absorption Fine‐Structure Technique and Microscopy of the Chemical State of Yttrium in α‐Polycrystalline Alumina

Yttrium‐doped a‐poly crystalline alumina was studied by microscopy observations and by extended X‐ray absorption fine‐structure experiments. The latter results were compared to those obtained for a standard Y 2 O 3 powder and to theoretical spectra for Y 2 O 3 , and Y 3 Al 5 O 12 calculated on the basis of crystallographic data. Most of the yttrium in the doped alumina is precipitated as a Y 3 Al 5 O 12 phase. An observed threshold displacement involves a slight valence electron delocalization for the Y 3+ ion.