کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1490680 | 992330 | 2010 | 8 صفحه PDF | دانلود رایگان |
The oxygen deficient perovskites, Bi0.15Sr0.85-xAexCoO3-δ, x = 0 and Aex = Ba0.28, Ca0.17, were studied with in-situ neutron powder diffraction and combined TGA/DSC in order to investigate their behaviour at elevated temperatures in oxidising conditions. The phase stability of the I4/mmm supercell structure adopted by Bi0.15Sr0.85CoO3-δ is shown to be dependent on temperature and the oxygen content of the phase, with three structural events, at T ∼ 250, 590 and 880 °C, detected. The first transition occurs as the perovskite supercell vanishes due to oxygen absorption; the second transition is also associated with oxidation and involves the decomposition of the perovskite phase via an exothermic process to yield a dominant hexagonal phase. Finally, at T ∼ 900 °C the perovskite phase re-forms. For the Ba and Ca containing materials the decomposition to the hexagonal phase occurs at T ∼ 600 °C and ∼ 650 °C respectively. The presence of Ca at the A-site is found to stabilise the I4/mmm supercell structure in the range RT - 650 °C. The antiferromagnetic to paramagnetic transitions occur at TN ∼ 250 °C, TN ∼ 175 °C and TN ∼ 145 °C for the samples with Aex = Ba0.28, x = 0 and Aex = Ca0.17, respectively.
Journal: Materials Research Bulletin - Volume 45, Issue 12, December 2010, Pages 1875–1882