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Applying the Sestak-Berggren Model to Analyze Non-Isothermal Kinetics and Thermodynamics of LiMnPO4 Synthesized from NH4MnPO4·H2O and Li2CO3 |
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PP: 241-256 |
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doi:10.18576/ijtfst/140310
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Author(s) |
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Safya Taha,
E. R. Shaabn,
M. Moustafa Abdel-Rahim,
Abdelaziz M. Aboraia,
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Abstract |
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| This study details the synthesis, thermal characterization, and kinetic analysis of lithium manganese phosphate (LiMnPO4), a material of significant interest for energy storage applications. LiMnPO4 was synthesized through a multi-step process involving the precipitation of ammonium manganese phosphate hydrate (NH4 MnPO4 · H2 O) followed by a solid-state reaction with lithium carbonate (Li2CO3). The reaction conditions were optimized through thermogravimetric (TGA) and differential thermal analysis (DTA), identifying critical phase transformation temperatures. Calcination at 600 K, 730 K, and 840 K resulted in distinct crystalline phases, as confirmed by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Thermal behavior was further investigated to determine activation energies for phase transitions using the Kissinger-Akahira-Sunose (KAS) and Sˇesta ́k-Berggren (SB) models. The KAS analysis revealed activation energies of 137.95 and 318.70 kJ/mol for sequential phase transitions, corresponding to dehydration and LiMnPO4 formation. FTIR analysis demonstrated significant changes in vibrational modes, indicating structural evolution during heating. SB modeling effectively described the reaction kinetics, providing insights into nucleation and growth mechanisms, with kinetic parameters suggesting three-dimensional volume nucleation as the dominant mechanism. These findings elucidate the thermal and kinetic characteristics of NH4 MnPO4 · H2 O to LiMnPO4 conversion, offering a robust framework for optimizing synthesis conditions and improving material performance for electrochemical applications. |
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