crystallize in the monoclinic described a phase formulated as ȁ1.4Bi 2 O 3 -MoO 3 having system, space group P2/c with a ؍ 11.742( 8) A ˚, b ؍ 5.800(7) a solid solubility, while Miyazawa et al. (11) presented A ˚, c ؍ 24.77(5) A ˚,  ؍ 102.94(6)؇, Z ؍ 1 and a ؍ 11.633(7) a new congruently melting compound with Bi/Mo ϭ 3, A ˚, b ؍ 5.795(3) A ˚, c ؍ 24.39(2) A ˚,  ؍ 101.35(5)؇, Z ؍ 1, formulated as 3Bi 2 O 3 -2MoO 3 in spite of a chemical analyrespectively. The structures were solved from 4242 and 3614 sis yielding Bi/Mo Х 2.6. The existence of a solid solution reflections, respectively, collected on a Philips PW1100 autoextending around the 1.3Bi 2 O 3 -MoO 3 composition was matic diffractometer (MoK␣ radiation). The final R indexes then confirmed by Chen and Smith (7). are 0.048 and 0.041. The common structure consists of [Bi 12 O 14 ] ؕ More recently, the phase diagram of the Bi 2 O 3 -MoO 3 columns along the twofold axis, connected with MoO 4 or binary system was reinvestigated by Egashira et al. (8) who (Mo, V)O 4 tetrahedra and isolated bismuth atoms in a quasiproposed two polymorphs for 3Bi 2 O 3 -2MoO 3 , related by planar O environment. A solid solution domain belonging to a phase transition at 750ЊC. Last, Buttrey et al. (9) conthis structural type within the Bi 2 O 3 -MoO 3 -V 2 O 5 ternary diagram has been evidenced. It extends from Bi 25.75 Mo 10 O ␦ to Bi 27.75 firmed the 3Bi 2 O 3 -2MoO 3 phase described as a defect Mo 10 O ␦ on the Bi 2 O 3 -MoO 3 line. This work was completed by fluorite structure. a preliminary study of conduction properties.