A MIXED-VALENT TITANIUM DIPHOSPHATE WITH AN INTERSECTING TUNNEL STRUCTURE - K0.58TIP2O7

A new mixed valent titanium diphosphate K0.58TiP2O7, has been isolated. It crystallizes in the space group C2/c with a = 17.852(2) Å, b = 6.298(1) Å, c = 12.181(2) Å, β = 119.73(1)°. Its [TiP2O7]∞ framework consists of corner-sharing TiO6 octahedra and P2O7 groups forming tunnels running along [010], [001], and [101]. This structure can be described either from TiP2O11 units characteristic of many diphosphates AxM P2O7, or from [TiPO8]∞ encountered in many monophosphates. The K+ ions are distributed over two kinds of sites, K(1) with a flattened octahedral coordination, and K(2) with a strongly distorted cubic coordination. The low occupancy of the second kind of site (16%) suggests the possibility of a wide of nonstoichiometry. © 1994 Academic Press, Inc.