| Abstract
| - Lithium zirconates, Li2ZrO3 and Li6Zr2O7, were synthesized by solid-state reaction. The thermal analysesof Li6Zr2O7 showed a continuous decomposition process due to lithium sublimation. However, the thermalbehavior of this compound changed slightly when different gas environments were used. If nitrogen wasused, Li6Zr2O7 decomposed in a mixture of Li2ZrO3, ZrO2, and Li2O(g). Nevertheless, air environmentproduced a different and more complex decomposition mechanism at high temperatures. In this case,lithium reacted with the oxygen from the air to produce Li2O at the surface, producing a temporaryincrease of the total weight. Subsequently, Li2O and some oxygen, from the Li6Zr2O7 structure, sublimedto produce Li2ZrO3 and ZrO2. The CO2 absorption capacity of both zirconates was studied. The materialsabsorbed CO2 at around the same temperature, 450−650 °C. Still, Li6Zr2O7 absorbed 4 times more CO2than Li2ZrO3. Furthermore, the CO2 sorption rate of Li2ZrO3 was much slower than that of Li6Zr2O7 atshort times. Apparently, at the beginning of the absorption process, there was more lithium available toreact with CO2 in the Li6Zr2O7 sample, as expected, although the sorption rates of both ceramics becamesimilar after long times. A correlation is established between the lithium and CO2 diffusion through theLi2CO3 produced on the surface of the particles. The best temperature for the CO2 absorption on Li6Zr2O7 was 550 °C. Finally, XRD analyses, after the CO2 absorption, and cyclic thermogravimetric analysesshowed that Li6Zr2O7 was not regenerated. In all cases, the final product was Li2ZrO3.
- Li6Zr2O7 was prepared by solid-state reaction. The thermal stability of this compound was then analyzed under different gas environments. The results were supported by a theoretical study. However, the carbon dioxide (CO2) absorption on this material was investigated. The results showed that Li6Zr2O7 has better CO2 absorption properties than other lithium ceramics. Finally, two different mechanisms for the thermal decomposition and CO2 absorption were proposed.
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