Single-phase　polycrystalline　solid　solutions　(La1-xSmx)B-6　(x=0,　0.2,　0.4,　0.8,　1)　are　fabricated　by　spark　plasma　sintering　(SPS).　This　study　demonstrates　a　systematic　investigation　of　structure-property　relationships　in　Sm-doped　LaB6　ternary　rare-earth　hexaborides.　The　microstructure,　crystallographic　orientation,　electrical　resistivity,　and　thermionic　emission　performance　of　these　compounds　are　investigated.　Analysis　of　the　results　indicates　that　samarium　(Sm)　doping　has　a　noticeable　effect　on　the　structure　and　performance　of　lanthanum　hexaboride　(LaB6).　The　analytical　investigation　of　the　electron　backscatter　diffraction　confirms　that　(La0.6Sm0.4)B-6　exhibits　a　clear　(001)　texture　that　results　in　a　low　work　function.　Work　functions　are　determined　by　pulsed　thermionic　diode　measurements　at　1500-1873K.　The　(La0.6Sm0.4)B-6　possesses　improved　thermionic　emission　properties　compared　to　LaB6.　The　current　density　of　(La0.6Sm0.4)B-6　is　42.4Acm(-2)　at　1873K,　which　is　17.5%　larger　than　that　of　LaB6.　The　values　of　phi(R)　for　(La0.6Sm0.4)B-6　and　LaB6　are　1.98　+/-　0.03　and　1.67　+/-　0.03eV,　respectively.　Furthermore,　the　Sm　substitution　of　lanthanum　(La)　effectively　increases　the　electrical　resistivity.　These　results　reveal　that　Sm　doping　lead　to　significantly　enhanced　thermionic　emission　properties　of　LaB6.　The　compound　(La0.6Sm0.4)B-6　appears　most　promising　as　a　future　emitter　material.