Alumina　powders　were　processed　with　7.8　wt%　CuO　and　post-sintering　reduction　heat-treatments　were　applied　with　the　aim　of　producing　metallic　grain　boundary　complexions.　The　influence　of　titanium　co-doping　was　also　studied.　Grain　boundaries　were　characterized　by　aberration-corrected　scanning　transmission　electron　microscopy.　Copper　grain　boundary　enrichment　was　achieved,　but　only　in　the　titanium　doped　samples;　the　segregated　copper　exhibited　a　Cu2+　valency　state,　the　segregated　titanium　exhibited　Ti3+　or　Ti4+　valency　states,　and　metallic　Cu　nanoparticles　were　also　observed.　The　crystallographic　orientation　of　the　grain　boundary　plane　had　a　marked　influence　on　concentration　and　oxidation　state　of　the　segregating　species.　(C)　2018　Published　by　Elsevier　Ltd　on　behalf　of　Acta　Materialia　Inc.