Abstract: The molybdenum(Ⅳ)oxides of formula Ln₂Mo₃O₉ were obtained by reduction of α-Ln₂Mo₃O₁₂(Ln=La,Pr,Nd, Sm,Gd,Dy)as well as Ce₂Mo₃O_12.25 in hydrogen at 500～650℃ for 60 hours,The compounds are of single phase and crystallize in tetragonal structurewith parameters a=0.5260nm～0.5131nm and c=1.18211nm¹.1122nm. There are twobroad absorption bands in the IR spectra of the Ln₂Mo₃O₉.All of the compounds are ^n-typesemiconductors with ρ_r.t.=92.13Ωcm～7.51Ωcm. Their electrical properties at 10～350℃and magnetic properties at 100～250K were measured.

Key words: rare earth molybdate, structure, electrical property, magnetic property