Bi 7−x As 1+x Mo 3 O 21 (0 x 1) a new pillar structure type: synthesis, crystal structure and conductivity Abstract An original structure of chemical formula Bi 13 As 3 Mo 6 O 42 has been obtained in the system Bi 2 O 3 :MoO 3 :As 2 O 3 by chemical transport reaction in presence of As 2 O 3. It crystallizes in the monoclinic system, space group P 2 1 /n with a = 12.7770(11) Å, b = 5.5890(4) Å, c = 27.971(2) Å and β = 101.009(7) •. The structure exhibits infinite [Bi 13 As 3 Mo 6 O 42 ] n complex pillars with a quite different organization compared with original [Bi 12 O 14 ] 8n+ n columns surrounded by (MoO 4) tetrahedra in the Bi 2/3 [Bi 12 O 14 ](MoO 4) 5 prototype structure. Nevertheless, the heavy atoms design almost perfect fluorite subnetwork-a common structural feature of these pillar structures. The conditions of synthesis via solid-state chemistry using basic oxides Bi 2 O 3 , As 2 O 3 and MoO 3 have been established and the phase identified by X-ray powder pattern. The indexing fits single crystal data as well as the values of volumic mass, ρ exp = 7.04(4) g cm −3 for ρ X = 7.096 g cm −3 for Z = 4. This Bi 13 As 3 Mo 6 O 42 phase shows also an interesting anionic conductivity around σ = 7.98 × 10 −4 S cm −1 at 980 K and is compared with related phases.  2004 Elsevier SAS. All rights reserved.