Heat capacity (Cp) and entropy of olivine-type LiFePO4 in the temperature range (2 to 773) K. (June 2015)

• Record Type: Journal Article
• Authors: Loos, Stefan; Gruner, Daniel; Abdel-Hafiez, Mahmoud; Seidel, Jürgen; Hüttl, Regina; Wolter, Anja U.B.; Bohmhammel, Klaus; Mertens, Florian
• Is Part Of: Journal of chemical thermodynamics. Volume 85(2015:Jun.)
• Page Start: 77
• Page End: 85
• Publication Date: 2015-06
• Subjects: Heat capacity -- LiFePO4 -- Entropy -- Antiferromagnetic transition -- Thermodynamics; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2015.01.007
• Languages: English
• ISSNs: 0021-9614

Abstract

Highlights: The heat capacity of olivine-type LiFePO4 was determined in the range of T = (2 to 773) K. The experimental data were found to be in good agreement with published theoretical calculations in a broad temperature range. The standard entropy of LiFePO4 has been calculated taking into account the antiferromagnetic transition at T = 49.2 K. Abstract: The heat capacity of olivine-type lithium iron phosphate (LiFePO4 – LFP) has been measured covering a temperature range from (2 to 773) K. Three different calorimeters were used. The Physical Property Measurement System (PPMS) from Quantum Design was applied in the range between T = (2 and 300) K, a Micro-DSC II from Setaram within the range between T = (283 and 353) K and data between T = (278 and 773) K were measured by means of a Sensys DSC (Setaram) using the Cp -by-step method. Experimental data are given with an error of (1 to 2)% above T = 20 K and up to 8% below 20 K. The data were subdivided into appropriate temperature intervals and fitted using common heat capacity functions. The low temperature results permit the calculation of standard entropies and temperature coefficients of electronic, lattice, as well as magnetic (antiferromagnetic transition at T = 49.2 K) contributions to the heat capacity. The obtained experimental values were compared to results of a recently published first principles phonon study (DFT) and to few available experimental data from the literature.