Mineo Sato, J. Abo, T. Jin
Oct 1, 1992
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Influential Citations
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Journal
Solid State Ionics
Abstract
Abstract The synthesis of NaLaNb2O7·xH2O was performed by the soft chemistry using an ion-exchange reaction of KLaNb2O7 powder with NaNO3 molten salt. The thermal stability of NaLaNb2O7·xH2O was examined by DTA and TG analyses. The crystal structures of hydrate and anhydrate forms of this compound were solved using X-ray powder diffraction data. The cell is tetragonal (space group I4 mm, Z=2) with a=3.8981 (1) A and c=25.7131 (9) A for the hydrate form, and is tetragonal (space group I4/m m m, Z=2) with a=3.9022 (1) A and c=21.1826 (8) A for the anhydrate form. Their structures were refined using a Rietveld refinement method. Both crystal structures are built up from a double layer of perovskite units, LaNb2O7, and the sodium atoms located between the layers. The sodium atoms of the hydrate form are in two crystallographic independent sites, while those of the anhydrous form are in an almost perfect tetrahedral site. These structural differences are discussed based on the hydrogen bond among the water molecules inserted in the layers.