Synthesis, Proton Exchange, and Topochemical Dehydration of New Ruddlesden-Popper Tantalates and Titanotantalates

Several new ion-exchangeable Ruddlesden-Popper phases were synthesized and characterized. K2CaNaTa3O10, which crystallizes in space group I4/mmm and has lattice constants of a=3.9185(1) and c=29.519(2), is the first all-tantalum(V) analogue of K2La2Ti3O10. K2Ca2Ta2TiO10 immediately hydrates in air to K2Ca2Ta2TiO10·0.8H2O, which belongs to space group P4/mmm with a=3.8903(1) and c=16.709(1). K2SrLaTi2TaO10·2H2O, which contains a large perovskite impurity, also crystallizes in space group P4/mmm and has lattice constants of a=3.9028(3) and c=16.896(2). All of the phases undergo ion exchange in dilute acid to form the corresponding solid acids. The solid acids topochemically dehydrate around 500°C to form A-site defective cubic perovskites.