STRUCTURE DETERMINATION OF KLANB2O7 EXHIBITING ION-EXCHANGE ABILITY BY X-RAY-POWDER DIFFRACTION

The crystal structure of KLaNb2O7 has been determined from X-ray powder diffraction data. The cell exhibits orthorhombic symmetry and belongs to C222 space-group with a = 3.9060(1) angstrom, b = 21.6031(7) angstrom, c = 3.8879(1) angstrom and Z = 2. The structure was refined using a Rietveld profile refinement method. The final reliability factors achieved were R(WP) = 0.0954, R(P) = 0.0676, R(I) = 0.0290 and R(F) = 0.0152. The structure is built up from double perovskite layers, LaNb2O7, interleaved by potassium atoms. The potassium ions were found to be statistically distributed at an interlayer site with an occupation factor of about 0.5. The ion exchange ability of this compound is discussed on the basis of the crystal structure.