Thermodynamic studies on lithium ferrites
Abstract
Thermodynamic studies on ternary oxides of Li-Fe-O systems were carried out using differential scanning calorimetry, Knudsen effusion mass spectrometry, and solid-state electrochemical technique based on fluoride electrolyte. Heat capacities of LiFe 5O 8(s) and LiFeO 2(s) were determined in the temperature range 127-861 K using differential scanning calorimetry. Gibbs energies of formation of LiFe 5O 8(s) and LiFeO 2(s) were determined using Knudsen effusion mass spectrometry and solid-state galvanic cell technique. The combined least squares fits can be represented as Δ fGmo(LiFe 5O 8,s, T)/kJ mol -1 (±6)=-2341+0.6764( T/K) (588≤ T/K≤971) Δ fGmo(LiFeO 2,s, T)/kJ mol -1 (±3)=-708+0.1656( T/K) (569≤ T/K≤1021) The temperature independent term of the above equations represents Δ fHom( Tav) and temperature dependent term represents negative change in entropy of the respective compounds. Thermodynamic analysis shows that LiFe 5O 8(s) is more stable compared to LiFeO 2(s).
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- May 2011
- DOI:
- 10.1016/j.jssc.2011.03.033
- Bibcode:
- 2011JSSCh.184.1186R