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Phase transition of RbH2PO4 and its composite with SiO2 studied by thermal analysis

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Abstract

The phase transition at T p (~109 °C) of RbH2PO4 and its composite with SiO2 has been investigated by thermal analysis here. In the case of neat RbH2PO4, there is a linear relationship between endothermic peak temperature (T m) and square root of heating rate (Φ 1/2), from which the onset temperature of phase transition can be determined. Besides, Kissinger method and another calculation method were employed to obtain the activation energy of phase transition. The detailed deduction process was presented in this paper, and the estimated activation energies are E 1 ≈ 126.3 kJ/mol and E 2 ≈ 129.2 kJ/mol, respectively. On the other hand, the heterogeneous doping of RbH2PO4 with SiO2 as dopant facilitates its proton conduction and leads to the disappearance of jump in conductivity at T p. The heats of transition in the composites decrease gradually with increasing the molar fraction of SiO2 additives. In the cooling process, a new and broad exothermic peak appeared between ~95 and ~110 °C, and its intensity also changes with the SiO2 amount. These phenomena might be related to the formation of amorphous phase of RbH2PO4 on the surface of SiO2 particles due to the strong interface interaction.

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Acknowledgements

The authors are very grateful to Prof. Tongbor Tang for his kind help. This work is supported financially by the Research Grant Council of Hong Kong (HKBU 210907).

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  1. Department of Physics, Hong Kong Baptist University, 224 Waterloo Road, Kowloon, Hong Kong, China

    Zikun Li & Wingkin Edward Chan

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  1. Zikun Li
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Correspondence to Zikun Li.

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Li, Z., Chan, W.E. Phase transition of RbH2PO4 and its composite with SiO2 studied by thermal analysis. J Therm Anal Calorim 104, 585–592 (2011). https://doi.org/10.1007/s10973-010-1005-4

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  • DOI: https://doi.org/10.1007/s10973-010-1005-4

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