Abstract: A novel method for the synthesis of ternary divalent rare earth iodides is reported. This method has a number of advantages. Among them are convenience in operation, less time-cost, and avoiding separately preparing the air-and moisture-sensitive REI₃or REI₂compounds. It is successful in synthesis of special divalent iodides which is difficult to be separated from the tervalent ones formed concomitantly. By using this method RbTml₃, KTmI₃, Cs₂TmI₄, TlSm₂I₅and KSm₂I₅, were synthesized. Their properties and structures were also determined. The structures of RbTml₃and KTmI₃belong to orthorhombic system, α=0. 8404 nm, 6= 1. 746 nm, c=1. 1797 nm, and α=0. 8057 nm, 6 = 1. 712 nm, c=1. 1137 nm,respectively. Space group is Pmmm. TlSm₂I₅is monoclinic system and α= 1. 002 nm, 6=0. 8910 nm, c=1. 4165 nm,β=90. 99. It is isomorphous with NH₄Pb₂Cls, space group P2₁/c. Cs₂TmI₄shows tetragonal system and α=0. 8967 nm, c=1.1207 nm. Its space group might be assigned to be P4/mmm.

Key words: Rare earth iodides, One-step synthesis, Structure