Dopant Distributions in Rare‐Earth‐Doped Alumina

The distribution of yttrium and lanthanum dopants has been mapped in yttrium‐ and lanthanum‐doped polycrystalline aluminas using imaging secondary‐ion mass spectrometry (imaging‐SIMS). Both dopants segregate to grain boundaries and pore surfaces. On average, yttrium occupies 7.1%–9.0% of the available grain‐boundary cation sites, whereas lanthanum occupies only 2.0%–5.2%. In 1000‐ppm‐yttrium‐doped alumina, an abundance of yttrium aluminum garnet precipitates also is observed. Implications of these observations to the creep behavior of alumina are discussed. The similarity in the segregation behavior of yttrium and lanthanum highlights the potential of lanthanum‐doped alumina for improved creep properties.