I had checked the thermal properties of Zinc Ferrite through TGA from room temperature to 800C , however according the TGA graph , there are still weight loss after 800C. Can anyone of you explain the possible causes or scientific explanation for the continuous weight loss at high temp.
Hello dear despite that I don't know which atmosphere was used by you. I can infer that during the process are produce differents oxides between them Fe3O4, Fe2O3 whose thermal stability are high. In the case of Zn, can be observed differents oxides whose phases are different. Therefore your thermal stability also will be different. These thermal stabilities are higher than 800 °C.
You may find the answer of your question from this paper:
http://www.sciencedirect.com/science/article/pii/S0304885314000572
http://www.sciencedirect.com/science/article/pii/S1878029612006354
"The stochastic geometric model was applied to kinetic modeling the complex process of thermal decomposition of zinc ferrite from neutral leach residues, at different operating temperatures (600 °C, 750 °C, 950 °C and 1150 °C). Based on functional dependence of Avrami׳s constant (n) in a function of the effective activation energy (Ea), it was found that at T>950 °C, the crystallization process takes place in autocatalytic stage, under the conditions where the rate of nucleation rapidly increases. It was established that the high nucleation rate can be attributed to formation of both Zn and Fe rich regions which provide a high number of heterogeneous nucleation sites. Based on the obtained final shape of the particles, it was found a strong presence of zinc, iron (present only in the form of Fe3O4 (magnetite)), magnesium (in the form of Mg2Si2O6), and also lead oxides. Thermodynamic analysis showed that the decomposition depends on the introduction of heat, and exerts a positive value of the Gibbs free energy of activation. Such a feature was expected since the ferrite system has been submitted to a forced decomposition and volatilization reactions."
It may be worth to check previous discussions ― concerned with possible experimental artifact contributions that may be encountered at the thermogravimetric analysis (TGA) of ferrite samples: https://www.researchgate.net/post/Analysis_of_TGA_of_ferrite_prepared_by_glycine_method https://www.researchgate.net/post/Unusual_weight_gain_loss_in_the_TG_thermogram_of_the_same_sample_on_different_TG_systems-any_thoughts/4
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