Highly crystalline niobium oxide converted from flux-grown K 4Nb6O17 crystals

Sunhyung Lee, Katsuya Teshima, Yuki Niina, Sayaka Suzuki, Kunio Yubuta, Toetsu Shishido, Morinobu Endo, Shuji Oishi

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Highly crystalline niobium oxide (Nb2O5) nanotubes without defects such as bent and node were successfully prepared by a two-step process. The first step entails making high quality, layered K 4Nb6O17 crystals as a precursor material. In this study, well-developed, highly crystalline, layered K4Nb 6O17 crystals were readily grown by the rapid cooling of a KCl flux at a holding temperature of 800 °C and a cooling rate of 300 °C h-1. The grown layered crystals of K4Nb 6O17 were transparent-colorless and had a median diameter of 530 nm. They were plate-like with well-developed faces. The second step is to transform the layered K4Nb6O17 crystals into highly crystalline Nb2O5 nanotubes. In order to make the nanotubes, an intercalation-exfoliation process using tetra(n-butyl)ammonium hydroxide (TBA+OH-) aqueous solution was carried out, and highly crystalline Nb2O5 nanotubes having a uniform diameter were successfully fabricated in this medhod. The crystallinity, uniformity and size (diameter and length) of nanotubes were significantly dependent on those of the precursor crystals. The flux-grown crystals, therefore, played a very important role in the nanotube fabrication. The average length and outer diameter were, respectively, about 100-500 nm and 15-25 nm. The photocatalytic properties of the layered K4Nb6O 17 crystals and the Nb2O5 nanotubes were basically almost the same, although their Brunauer-Emmett-Teller (BET) surface areas were quite different from each other. The BET surface area of the Nb 2O5 nanotubes (108.71 m2 g-1) was ca 20 times larger than that of the layered K4Nb6O 17 crystals (5.14 m2 g-1). As compared with the flux-grown K4Nb6O17 crystals, the Nb 2O5 nanotubes exhibited high photocatalytic activity for the photodegradation of trichloroethylene. The grown layered K 4Nb6O17 crystals and Nb2O 5 nanotubes were investigated thoroughly by means of field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction analysis, energy-dispersive X-ray spectrometry, BET surface area and pore size distribution analysis, and spectrophotometry.

Original languageEnglish
Pages (from-to)2326-2331
Number of pages6
Issue number11
Publication statusPublished - 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics


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