e., approximately 20 M), all of the Na+ appeared to be involved in the exchange with Li+ in Na2Nb2O6-H2O. Figure 1a compares the XRD pattern of Li2Nb2O6-H2O and Na2Nb2O6-H2O. The overall XRD pattern of Li2Nb2O6-H2O was quite different from that of Na2Nb2O6-H2O. From an inductive-coupled Selleck Y 27632 plasma (ICP) measurement of Li2Nb2O6-H2O, we did not find any trace of Na+ within the experimental limits. These results imply that crystalline Li2Nb2O6-H2O could be obtained from Na2Nb2O6-H2O through an ion exchange process.
Figure 1 Phase PHA-848125 transformation from Li 2 Nb 2 O 6 -H 2 O to LiNbO 3 . High-resolution X-ray diffraction (HR-XRD) patterns of Li2Nb2O6-H2O at (a) room temperature and (b) elevated temperatures. In (a), we show the XRD patterns of Na2Nb2O6-H2O and LiNbO3 for comparison. (c) Thermogravimetric (TG) and differential scanning calorimetry (DSC) results for Li2Nb2O6-H2O. In Figure 1b, we show in-situ XRD patterns of Li2Nb2O6-H2O at elevated temperatures. The diffraction patterns of Li2Nb2O6-H2O were significantly modified with an increase in temperature, especially above 400°C, and exhibited see more an irreversible phase transformation. In the inset of Figure 1a, we show the XRD pattern after heat treatment of Li2Nb2O6-H2O.
We note that the XRD pattern obtained after heat treatment was well indexed by LiNbO3. To the best of our knowledge, this is the first report for the synthesis of LiNbO3 nanowire through ion exchange and subsequent heat treatment. To gain insight into the phase transformation from Li2Nb2O6-H2O to LiNbO3, we show the thermogravimetric (TG) and differential
scanning calorimetry (DSC) results Dynein in Figure 1c. The mass of Li2Nb2O6-H2O changed significantly near 400°C and was accompanied by endothermic reactions at the same temperature. After the endothermic reactions, an exothermic reaction occurred near 460°C without a noticeable change in the mass. Comparing the well-known phase transformation mechanism from Na2Nb2O6-H2O to NaNbO3, the peaks at 400°C and 460°C corresponded well to the dehydration of H2O from Li2Nb2O6-H2O and the structural transformation from Li2Nb2O6 to LiNbO3, respectively. (The broad change in the mass near 220°C seems to have originated from the desorption of surface/lattice-absorbed hydroxyl defects ). Due to the light Li ions, we used neutrons rather than X-rays to determine the detailed crystal structure of LiNbO3. Figure 2a shows a Rietveld analysis of the neutron diffraction pattern of LiNbO3. The neutron diffraction pattern of LiNbO3 was well-fit by the trigonal structure (a = 5.488 Å, α = 55.89°) with R3c symmetry. The resulting lattice constant (angle) of the LiNbO3 nanostructure was slightly smaller (larger) than that of the LiNbO3 single crystal (a = 5.492 Å, α = 55.53°) . Based on the Rietveld analysis, we show the crystal structure of LiNbO3 in the inset of Figure 2a.