In situ observation of dehydration-induced phase transformation from Na 2Nb 2O 6-H 2O to NaNbO 3

Jong Hoon Jung*, Chih Yen Chen, Wen-Wei Wu, Jung Il Hong, Byung Kil Yun, Yusheng Zhou, Nuri Lee, William Jo, Lih Juann Chen, Li Jen Chou, Zhong Lin Wang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


We have monitored the phase transformation from a Sandia octahedral molecular sieve Na 2Nb 2O 6-H 2O to a piezoelectric NaNbO 3 nanowire through in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements at high temperatures. After dehydration at 288 °C, the Na 2Nb 2O 6-H 2O becomes significantly destabilized and transforms into NaNbO 3 with the increase of time. The phase transformation time is exponentially proportional to the inverse of temperature, for example, ∼10 5 s at 300 °C and ∼10 1 s at 500 °C, and follows an Arrhenius equation with the activation energy of 2.0 eV. Real time TEM investigation directly reveals that the phase transformation occurs through a thermally excited atomic rearrangement due to the small difference of Gibbs free energy between two phases. This work may provide a clue of kinetic control for the development of high piezoelectric lead-free alkaline niobates and a deep insight for the crystallization of oxide nanostructures during a hydrothermal process.

Original languageEnglish
Pages (from-to)22261-22265
Number of pages5
JournalJournal of Physical Chemistry C
Issue number42
StatePublished - 25 Oct 2012

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