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Published February 24, 2010 | public
Journal Article

Examination of the superprotonic transition and dehydration behavior of Cs_(0.75)Rb_(0.25)H_2PO_4 by thermogravimetric and differential thermal analyses

Abstract

The dehydration and the superprotonic transition behavior of Cs_(0.75)Rb_(0.25)H_2PO_4 have been investigated via thermogravimetry and differential thermal analysis. To enable measurements under the high water partial pressures required, a high humidity system (p_(H_2O) = 0.02–0.8 atm) capable of weight change detection at 0.7% resolution and thermal events with 0.01 °C resolution was assembled. It has been found that the superprotonic phase transition temperature of Cs_(0.75)Rb_(0.25)H_2PO_4 is 231 °C, slightly higher than that of CsH_2PO_4. In contrast, dehydration of Cs_(0.75)Rb_(0.25)H_2PO_4 under p_(H_2O) = 0.35 atm occurs at 265 °C, a somewhat lower temperature than that at which CsH_2PO_4 undergoes dehydration. Analysis of the temporal evolution of both transformations suggests a mechanism of continuous nucleation of the high temperature phase at a constant nucleation rate combined with three-dimensional growth.

Additional Information

© 2009 Elsevier B.V. Received 20 August 2008; revised 26 September 2009; accepted 26 October 2009. Available online 17 November 2009. The authors gratefully acknowledge Mary Louie for providing EDS chemical analysis results. This work has been funded by a Department of Defense MURI award administered by the Army Research Office (W911NF-07-1-0410). Additional support has been provided by the National Science Foundation (DMR-0520565), through the Caltech Center for the Science and Engineering of Materials.

Additional details

Created:
August 21, 2023
Modified:
October 20, 2023