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The NaNO3-KNO3 system: the postion of the solidus and sub-solidus

Record type: Article

The existing evidence for the nature of the phase diagram for the binary system sodium nitrate–potassium nitrate is reviewed and in particular whether the system is of the continuous solid solution type, as has often been stated in the last 80 years, or whether this system is of the eutectic type as was earlier believed and has again been asserted recently. Additional evidence from Raman spectroscopy and Raman mapping on the 50 50 mol%(minimum melting point) composition is now presented, supporting the eutectic classification. Abrupt changes in wavenumber, or in the wavenumber–temperature gradient of five Raman bands indicate a solid-state transition at about 115 °C and are attributed to a phase transition in KNO3-rich areas. On a fast cooled sample, Raman bands attributed to sodium nitrate-rich and potassium nitrate-rich areas were found to persist up to and slightly beyond the melting point, and although their wavenumber-positions converged, the apparent single band could still be resolved into the two bands which could be attributed to the Na-rich and K-rich areas. On cooling, the reverse change took place quickly. Measurements with the initially slow cooled sample, where these areas were bigger, showed that the spectral bands reverted to the room-temperature wavenumber values, after holding at 22 °C for only 60–90 min.

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Citation

Berg, Rolf W. and Kerridge, David H. (2004) The NaNO3-KNO3 system: the postion of the solidus and sub-solidus Dalton Transactions, 15, pp. 2224-2229. (doi:10.1039/B403260H).

More information

Published date: 2004

Identifiers

Local EPrints ID: 22827
URI: http://eprints.soton.ac.uk/id/eprint/22827
ISSN: 1477-9226
PURE UUID: 8f677c2e-c35c-45af-aa6f-b6adef4bbc17

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Date deposited: 20 Jun 2006
Last modified: 17 Jul 2017 16:20

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Contributors

Author: Rolf W. Berg
Author: David H. Kerridge

University divisions


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