6533b871fe1ef96bd12d2311

RESEARCH PRODUCT

Preparation and structural study of sodium germanium phosphate-sodium titanium phosphate solid solutions. I. Evolution of structure with composition

subject

description

Compounds NaM2IV(PO4)3 with M = Ge, Ti present the [NZP]-type structure, with a low thermal expansion. The space group at room temperature for the compound NaGe2(PO4)3 is R3, whereas for the compound NaTi2(PO4)3 is R3c. Evolution of the structure with composition in NaGe2(PO4)3  NaTi2(PO4)3 system is discussed. The space group and lattice parameters were determined for NaGe2−xTix(PO4)3 (0 < x < 2) solid solutions, prepared by ceramic method. Compositions rich in Ge(IV) (0 ≤ x ≤ 1) show the R3 space group, whereas for those rich in Ti(IV) (1.2 ≤ x ≤ 2) the space group is R3c. The variation of the lattice parameters with composition agreed with these results since it showed a change in its tendency between compositions with x = 1 and 1.2. Structure of NaGeTi(PO4)3 (x = 1 was determined by Rietveld method. It presents a R3 symmetry with an ordered distribution of the Ge(IV) and Ti(IV) atoms over two types of octahedra.