ON NEW MIXED CONDUCTORS OF BI4V2-XMNXO11-DELTA FORMULATION

The partial substitution of manganese for vanadium in the perovskite-l ike sheets of Bi4V2O11 has allowed to stabilize at room temperature th e structure of gamma-Bi4V2O11 for 0.15 less than or equal to x less th an or equal to 0.50. Magnetic measurements have shown that the mangane se offers simultaneously the +III and +IV oxidation states. It results that the materials prepared can be formulated: Bi4V2-xMx-y3+Mny4+O11- x+y/2 (delta=x-y/2). Study of electrical properties has revealed the p resence of a mixed contribution, at the same time electronic and ionic , in these materials. The conductivity of the (x=0.20) composition is mainly ionic and its value locates this material among the best ionic conductors or gamma-Bi4V2O11 structural type. (C) 1997 Elsevier Scienc e S.A.