As　an　alternative　for　thoriated　tungsten　thermionic　cathodes,　molybdenum　doped　with　either　a　single　rare　earth　oxide　such　as　La2O3,　Y2O3　and　Sc2O3　or　a　mixture　thereof　has　been　produced　by　powder　metallurgy.　It　is　shown　that　carbonization　can　greatly　improve　the　emission　properties　(i.e.　emission　capability　and　stability)　of　RE2O3　doped　molybdenum　due　to　the　formation　of　a　(metallic)　rare　earth　atomic　layer　on　the　surface　of　the　cathode　by　the　reduction　reaction　of　molybdenum　carbide　and　rare　earth　oxide.　Among　all　the　carbonized　samples,　La2O3　and　Y2O3　co-doped　molybdenum　cathode　showed　the　best　performance　in　emission.　In　addition,　computer　pattern　recognition　technique　has　been　used　to　optimize　the　composition　of　the　material　and　of　the　cathode　preparation　technique.　We　derive　the　equation　of　the　emission　efficiency　as　a　function　of　cathode　composition　and　carbonization　degree.　Based　on　the　projecting　coordinates　obtained　from　the　equation,　the　optimum　projection　region　was　identified,　which　can　serve　as　guide　for　the　composition　and　carbonization　degree　design.　(c)　2005　Elsevier　B.V.　All　rights　reserved.