MUTUAL INFLUENCE OF 3D AND 4F ATOMS IN K2NIF4-TYPE STRUCTURE DILUTED SOLID-SOLUTIONS Y1-XND(CE)(X)CACRYAL1-YO4 (X-LESS-THAN-OR-EQUAL-TO-0.1Y-LESS-THAN-OR-EQUAL-TO-0.1)

Diluted solid solutions of '3d' (chromium) and '4f' (neodymium and cer ium) elements in the K2NiF4-type 1/1 perovskite rock salt intergrowth structure of mixed aluminates were investigated in order to get eviden ce of mutual influence phenomena. Crystal chemical data obtained for t he solid solution Y1-xNdxCaCryAl1-yO4 (x less than or equal to 0.1; y less than or equal to 0.1) point to the existence of an Nd(III)-O-Cr(I II) coupling in the bridge bonds which connect the perovskite and rock salt slabs. A non-statistical distribution of Nd(III) is very likely to occur in the rock salt slabs. A magnetochemical characterization br ings the proof of a partial reduction of Ce(IV) to Ce(III) in the comp osition Y0.9Ce0.1CaAlO4, as in Y0.8Ce0.1Ca1.1AlO4 the only (IV) valenc e state is found. The simultaneous presence of Ce(IV) and Ce(III) is c onfirmed by the results of structure calculations, in terms of a split ting of the Ce-O distances in the rock salt slabs. (C) 1997 Elsevier S cience S.A.