Using non-isothermal thermogravimetry (TG), the oxidation kinetics of oxygen-deficient lithium–titanium ferrospinel, Li0.649Fe1.598Ti0.5Zn0.2Mn0.051O4−δ, manufactured by ceramic engineering is investigated. The oxidation annealing of powder samples is performed in air. According to the X-ray phase analysis, the processes giving rise to variations in oxygen content occur within single-phase spinel structure. The experimental kinetic results are processed using the Netzsch Thermokinetics software. The oxidation rate constants and the effective coefficients of atmospheric oxygen diffusion into the ferrites are determined. The effective activation energy E of oxygen diffusion is found to be 1.95 eV. It is demonstrated that an increase in the oxygen non-stoichiometry parameter δ as a result of recovery annealing of ferrite powders in vacuum at T = 1,070 K for 2 h gives rise to a slight decrease in E down to 1.89 eV. The activation energy of oxygen grain-boundary diffusion is identified by the electroconduction method. The resulting value 1.93 eV is fairly consistent with that obtained by TG.
1. Levin BE , Tret'yakov YD, Letyuk LM. Physicochemical principles of preparation, properties, and applications of ferrites. Moscow: Metallurgiya; 1979 (in Russian).
2. Valenzuela, R 1994 Magnetic ceramics Cambridge University Press Cambridge .
3. West, AR 1988 Basic solid state chemistry Wiley New York.
4. Viswanathan, B, Murthy, VRK 1990 Ferrite materials science and technology Narosa Publishing House New Delhi.
5. Gundlach, EM, Gallagher, PK 1998 Thermogravimetric determination of the oxygen non-stoichiometry in Ni0.563Zn0.188Fe2.25O4+γ and Ni0.375Zn0.375Fe2.25O4+γ. Thermochim Acta 318:15–20 .
6. Surzhikov, AP, Pritulov, AM, Ghyngazov, SA, Lysenko, EN 1999 Investigation of oxygen diffusion in Li-Ti ferrites. Perspektivniye Materialy 6:90.
7. Surzhikov, AP, Lysenko, EN, Ghyngazov, SA, Frangulyan, TS 2002 Determination of the oxygen diffusion coefficient in polycrystalline Li-Ti ferrites. Rus Phys J 45:989 .
8. Sanders, JP, Gallagher, PK 2003 Kinetics of the oxidation of magnetite using simultaneous TG/DSC. J Therm Anal Calorim 72:777–89 .
9. Vourlias, G, Pistofidis, N, Pavlidou, E, Chrissafis, K 2009 Oxidation behaviour of precipitation hardened steel TG, X-Ray, XRD and SEM study. J Therm Anal Calorim 95:63–8 .
10. Kalogirou, M, Samaras, Z 2010 Soot oxidation kinetics from TG experiments. J Therm Anal Calorim 99:1005–10 .
11. Amankwah, RK, Pickles, CA 2009 Thermodynamic, thermogravimetric and permittivity studies of hausmannite (Mn3O4) in air. J Therm Anal Calorim 98:849–53 .
12. Ridgley, DH, Lessoff, H, Childress, JD 1970 Effects of lithium and oxygen losses on magnetic and crystallographic properties of spinel lithium ferrite. J Am Ceram Soc 53:304–11 .
13. Opffermann, J 2000 Kinetic analysis using multivariate non-linear regression. J Therm Anal Calorim 60:641–58 .
14. Mianowski, A, Marecka, A 2009 The isokinetic effect as related to the activation energy for the gases diffusion in coal at ambient temperatures. Part I. Fick's diffusion parameter estimated from kinetic curves. J Therm Anal Calorim 95:285–92 .
15. Zhuravlev, GI, Golubkov, LA, Strazova, TA 1990 Main types of ferrite microstructure and their formation. Poroshkovaya Metallurgiya 6:68.
16. Surzhikov, AP, Peshev, VV, Pritulov, AM, Ghyngazov, SA 1999 Grain-boundary oxygen diffusion in polycrystalline ferrites. Rus Phys J 42:490 .
17. Patent RU 2169914, G01N13/00; 1999.
18. Fisher, JC Calculation of diffusion penetration curves for surface and grain boundary diffusion. J Appl Phys 1951 22:74–7 .