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Issue 2, 2018
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Probing Co- and Fe-doped LaMO3 (M = Ga, Al) perovskites as thermal sensors

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The synthesis of a Co-doped or Fe-doped La(Ga,Al)O3 perovskite via the Pechini process aimed to achieve a color change induced by temperature and associated with spin crossover (SCO). In Fe-doped samples, iron was shown to be in the high-spin state, whereas SCO from the low-spin to the high-spin configuration was detected in Co-doped compounds when the temperature increased. Fe-doped compounds clearly adopted the high-spin configuration even down to 4 K on the basis of Mössbauer spectroscopic analysis. The original SCO phenomenon in the Co-doped compounds LaGa1−xCoxO3 (0 < x < 0.1) was evidenced and discussed on the basis of in situ X-ray diffraction analysis and UV-vis spectroscopy. This SCO is progressive as a function of temperature and occurs over a broad range of temperatures between roughly 300 °C and 600 °C. The determination of a crystal field strength of about 2 eV and a Racah parameter B of about 500 cm−1 for Co3+ (3d6) ions show that these values allow the occurrence of SCO. Hence, this study shows the possibility of using LaGa1−xCoxO3 compounds as thermal sensors at low Co contents (x = 0.02). The competition between steric and electronic effects in LaGaO3 in which Co3+ is stabilized in the LS state shows that electronic effects with the creation of M–O covalent bonds are predominant and contribute to the stabilization of a high crystal field around Co3+ (LS) although its ionic radius is smaller in comparison with that of Ga3+.

Graphical abstract: Probing Co- and Fe-doped LaMO3 (M = Ga, Al) perovskites as thermal sensors

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The article was received on 28 Sep 2017, accepted on 20 Nov 2017 and first published on 22 Nov 2017

Article type: Paper
DOI: 10.1039/C7DT03647G
Citation: Dalton Trans., 2018,47, 382-393
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    Probing Co- and Fe-doped LaMO3 (M = Ga, Al) perovskites as thermal sensors

    O. Toulemonde, A. Devoti, P. Rosa, P. Guionneau, M. Duttine, A. Wattiaux, E. Lebraud, N. Penin, R. Decourt, A. Fargues, S. Buffière, A. Demourgues and M. Gaudon, Dalton Trans., 2018, 47, 382
    DOI: 10.1039/C7DT03647G

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