Abstract
The oxygen adsorption and desorption of newly found compounds RBaCo 4O 7 (R = Y, Dy–Lu, In) were investigated by thermogravimetry (TG) in the temperature range from room temperature to 1100 °C. The influence of Co replaced by Zn and Fe on the oxygen diffusion properties of YBaCo 4O 7 was also studied. TG results showed clearly that all RBaCo 4O 7 compounds basically experience two oxygen adsorption and desorption processes in the temperature range 20∼1100 °C in oxygen flow. One happens at about 200∼450 °C and the another happens at about 660∼1050 °C. The differences between the resulting states by adsorbing oxygen at lower and high temperature were discussed based on the X-ray diffraction (XRD) patterns and TG data. We showed evidence that the oxygen adsorption at the lower temperature has a small activation energy, while the oxygen adsorption at the higher temperature has a large activation energy. The oxygen adsorbed at high temperature will destroy the RBaCo 4O 7 structure. Zn substituting in the YBaCo 4 − x Zn x O 7 influences the oxygen diffusion behavior prominently, the amount of oxygen adsorbed becomes increasingly weak with the increase of Zn content and disappears completely for the samples with x ≥ 2.0. However, replacement of Co by Fe has little effect on the oxygen absorption process.
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