PREPARATION AND STRUCTURE OF CERIUM TITANATES CE2TIO5, CE2TI2O7, AND CE4TI9O24

Compounds Ce2TiO5, Ce2Ti2O7, and Ce4Ti9O24 were prepared by heating ap propriate mixtures of solids containing Ce4+ and Ti3+ or Ti which were placed in a platinum-silica-ampoule combination at T = 1250-degrees-C (3d) under vacuum. The new compounds were characterized by powder pat terns. We obtained Ce2TiO5 which is isotypic to La2TiO5 and crystalliz es in the Y2TiO5-type (space group Pnma) with a = 10.877(6) angstrom, b = 3.893(1) angstrom, c = 11.389(8) angstrom, Z = 4. Ce2Ti2O7 is isot ypic to La2Ti2O7 and crystallizes in the monoclinic Ca2Nb2O7 type (spa ce group P 2(1)) with a = 7.776(6) angstrom, b = 5.515(4) angstrom, c = 12.999(6) angstrom, beta = 98.36(5), Z = 4. The compound Ce4Ti9O24 c rystallizes orthorhombic with a = 14.082(4) angstrom, b = 35.419(8) an gstrom, c = 14.516(4) angstrom, Z = 16. The new cerium titanate Ce4Ti9 O24 is isotypic to Nd4Ti9O24 (space group Fddd (No. 70)) which represe nts a novel type of structure. (C) 1994 Academic Press, Inc.