Ionic conduction in substituted scheelite-type oxides

In a search for new high temperature ionic conductors, various substituted scheelite-type samples were prepared by the solid state reaction and their electrical conduction was investigated Typical scheelite-type oxides design ated as ABO(4) (A = Ca, Sr, Ba; B = W, Mo) are generally classified into th e oxysalts. However, some oxides having cations with almost the same electr onegativities, such as Pb and W in PbWO4, can be regarded as double oxides with a deformed fluorite-type structure. Therefore, in order to create appr opriate conductors in each oxide type, A(2+)B(6+)O(4), alternative substitu tions were tried: A(1-x)M(2x)(+)BO(4) for the former and A(1-x)M(x)(3+)BO(4 +x/2) for the latter. As a result, new types of ionic conductors were found : lithium ion conductors and oxide ion conductors in scheelite-type solid s olutions based on ABO(4) (A = Ca, Sr, Ba; B = W, Mo) and PbWO4, respectivel y. Lithium ion conduction was confirmed visually by neutron radiography. (C ) 2000 Elsevier Science B.V. All rights reserved.