ISOMORPHOUS SUBSTITUTION IN KTIOPO4 - A SINGLE-CRYSTAL DIFFRACTION STUDY OF MEMBERS OF THE K1-XNAXTIOPO4 SOLID-SOLUTION

K0.42Na0.58TiOPO4 was prepared by sodium ion exchange into KTiOPO4 at 350-degrees-C. Crystal data: orthorhombic, Pn2(1)a(33), a = 12.7298 (21), b = 10.6073 (13), c = 6.3074 (4) angstrom, V = 851.7 angstrom3, Z = 4, D(c) = 2.942 g cm-3 , F(000) = 736. A sample was subsequently annealed at 700-degrees-C. The structure of the ion-exchanged material is very similar to that found after annealing and is also consistent with that obtained in an earlier powder diffraction and solid-state NMR study of K0.5Na0.5TiOPO4, confirming the validity of the powder work. There is considerable ordering over the two sites (site 1 0.933 (1) Na:0.067 (1) K; site 2 0.773 (7) K:0.227 (7) Na), and the single-crystal diffraction data are of sufficient resolution to detect the differing positions for the two cations on each site. Cation substitution does not affect the surrounding oxygen coordination sphere.