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In situ Precursor-Template Route to Semi-Ordered NaNbO 3 Nanobelt Arrays

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ABSTRACT

We exploited a precursor-template route to chemically synthesize NaNbO3 nanobelt arrays. Na7(H3O)Nb6O19·14H2O nanobelt precursor was firstly prepared via a hydrothermal synthetic route using Nb foil. The aspect ratio of the precursor is controllable facilely depending on the concentration of NaOH aqueous solution. The precursor was calcined in air to yield single-crystalline monoclinic NaNbO3 nanobelt arrays. The proposed scheme for NaNbO3 nanobelt formation starting from Nb metal may be extended to the chemical fabrication of more niobate arrays.

No MeSH data available.


a SEM image of the product prepared at 150–180°C for 20–24 h, indicating the coexistence of Na7(H3O)Nb6O19·14H2O nanobelts and NaNbO3 cubes. b NaNbO3 nanocube film obtained at 200–220°C for 18–24 h.
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Figure 8: a SEM image of the product prepared at 150–180°C for 20–24 h, indicating the coexistence of Na7(H3O)Nb6O19·14H2O nanobelts and NaNbO3 cubes. b NaNbO3 nanocube film obtained at 200–220°C for 18–24 h.

Mentions: All the above results reveal that the 1D characteristic of the precursor and the solid-state phase transformation process are all the important factors on the formation of perovskite NaNbO3 nanobelts. The existing 1D nanostructure serves as structural template from which NaNbO3 nanobelt can be readily generated. The size of the precursor is a critical determinant factor in governing the resultant shape of the final NaNbO3 product. Above a critical size, propagation of the reaction front is observed, and the basic morphology of the precursor is maintained [26]. During transformation process of the Na7(H3O)Nb6O19·14H2O nanobelt, the width of the reaction zone is not comparable to the size of this precursor, propagation of the reaction front can span, and the 1D nonequilibrium shape can be maintained. A second vital factor is post-temperature-induced phase transformation that drives oriented rearrangement of NaNbO3 nanoparticles into single-crystalline nanobelts. The precursor undergoes solid-phase reactions rather than continues to grow under hydrothermal circumstance, no dissolution and atom-by-atom recrystallization process happens, which prevents potential shape evolution of the 1D precursor. Therefore, perovskite formation in solution phase can be avoided using short treat time. Increase in reaction time results in lots of NaNbO3 cubes, as shown in Figure 8a. The controllable surface structures are further shown in Figure 8b. When increasing reaction temperature from 150–180 to 200–220°C, stable NaNbO3 perovskite is formed, and no 1D nanostructure is obtained. The higher temperature affords adequate energy to overcome the activation energy and the reaction barrier in the formation of perovskite structure. This also affords a facile way to change the surface structure of niobate films.


In situ Precursor-Template Route to Semi-Ordered NaNbO 3 Nanobelt Arrays
a SEM image of the product prepared at 150–180°C for 20–24 h, indicating the coexistence of Na7(H3O)Nb6O19·14H2O nanobelts and NaNbO3 cubes. b NaNbO3 nanocube film obtained at 200–220°C for 18–24 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC3211187&req=5

Figure 8: a SEM image of the product prepared at 150–180°C for 20–24 h, indicating the coexistence of Na7(H3O)Nb6O19·14H2O nanobelts and NaNbO3 cubes. b NaNbO3 nanocube film obtained at 200–220°C for 18–24 h.
Mentions: All the above results reveal that the 1D characteristic of the precursor and the solid-state phase transformation process are all the important factors on the formation of perovskite NaNbO3 nanobelts. The existing 1D nanostructure serves as structural template from which NaNbO3 nanobelt can be readily generated. The size of the precursor is a critical determinant factor in governing the resultant shape of the final NaNbO3 product. Above a critical size, propagation of the reaction front is observed, and the basic morphology of the precursor is maintained [26]. During transformation process of the Na7(H3O)Nb6O19·14H2O nanobelt, the width of the reaction zone is not comparable to the size of this precursor, propagation of the reaction front can span, and the 1D nonequilibrium shape can be maintained. A second vital factor is post-temperature-induced phase transformation that drives oriented rearrangement of NaNbO3 nanoparticles into single-crystalline nanobelts. The precursor undergoes solid-phase reactions rather than continues to grow under hydrothermal circumstance, no dissolution and atom-by-atom recrystallization process happens, which prevents potential shape evolution of the 1D precursor. Therefore, perovskite formation in solution phase can be avoided using short treat time. Increase in reaction time results in lots of NaNbO3 cubes, as shown in Figure 8a. The controllable surface structures are further shown in Figure 8b. When increasing reaction temperature from 150–180 to 200–220°C, stable NaNbO3 perovskite is formed, and no 1D nanostructure is obtained. The higher temperature affords adequate energy to overcome the activation energy and the reaction barrier in the formation of perovskite structure. This also affords a facile way to change the surface structure of niobate films.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We exploited a precursor-template route to chemically synthesize NaNbO3 nanobelt arrays. Na7(H3O)Nb6O19·14H2O nanobelt precursor was firstly prepared via a hydrothermal synthetic route using Nb foil. The aspect ratio of the precursor is controllable facilely depending on the concentration of NaOH aqueous solution. The precursor was calcined in air to yield single-crystalline monoclinic NaNbO3 nanobelt arrays. The proposed scheme for NaNbO3 nanobelt formation starting from Nb metal may be extended to the chemical fabrication of more niobate arrays.

No MeSH data available.