Thermoelectric　materials　formulated　with　LaxCo4Sb12　were　prepared　via　mechanical　alloying　(MA)　and　spark　plasma　sintering　(SPS).　The　regularities　of　their　thermoelectric　properties　varying　with　La　content　at　100-500　degrees　C　are　investigated.　The　experimental　results　show　that　the　La　doping　helps　achieve　the　P　or　N　type　semiconductor　materials　and　improves　their　thermoelectric　properties.　The　ZT　value　increases　with　La　content　(x)　from　0.1　to　0.9,　but　decreases　when　x　changes　from　0.9　to　2.0.　The　maximum　ZT　value　is　0.3425　when　x=0.9　at　500　degrees　C　and　the　optimal　doped　La　content　is　about　0.9-1.0　under　the　experimental　conditions　in　this　study.　(c)　2005　Elsevier　B.V.　All　rights　reserved.