Vaporization and Thermodynamic Properties of GdFeO 3 and GdCoO 3 Complex Oxides
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rization and Thermodynamic Properties of GdFeO3 and GdCoO3 Complex Oxides S. I. Lopatina,*, I. A. Zverevaa, and I. V. Chislovaa a St.
Petersburg State University, St. Petersburg, 199034 Russia *e-mail: [email protected]
Received March 26, 2020; revised March 26, 2020; accepted April 5, 2020
Abstract—The processes of gadolinium ferrite and gadolinium cobaltite vaporization was studied. It was shown that the predominant components of vapor are atomic iron and cobalt, which are characteristic for the vaporization of individual iron and cobalt oxides, respectively. The activities of iron and cobalt oxides in GdFeO3 and GdCoO3 were determined. Keywords: high-temperature mass spectrometry, vaporization, gadolinium ferrite, gadolinium cobaltite
DOI: 10.1134/S1070363220080174 Perovskite-like compounds have numerous useful functional properties and are used in the latest technologies [1]. Oxides with the perovskite structure are currently used in radiotechnics, electronics, and magnetooptic data storage [2, 3], as solid-state fuel cells [4], gas sensors [5–10], and in protection of the environment from the toxic action of industrial emissions [11]. Ferrites and cobaltites occupy a special place among numerous magnetic materials with the perovskite structure. Due to their magnetic properties, GdFeO3 can be used as a contrast agent in MRT, and the nanocomposite can be used for the drug delivery [12]. Recently, the prospect appears of ferrites and cobaltites practical use in catalysis and photocatalysis [13–15]. Traditionally such oxides are synthesized by ceramic technology, which requires a large economic cost (long synthesis duration and high calcination temperatures), besides it does not allow obtaining particles in the nanoscale range, which is important above all for catalytic activity. The search for new methods of synthesis of complex ferrites and cobaltites is ongoing. One of the most promising, economical, and environmentally friendly methods is the sol-gel method, which makes it possible to obtain ultra-dispersed powders, fibers, or thin films from solutions at lower temperatures than in the case of traditional solid-phase synthesis. For the synthesis of compounds with a complex cationic composition, the sol-gel method has not been sufficiently studied, it
requires significant development of individual stages and the search for optimal synthesis conditions. When the ferrites and cobaltites are synthesized in one way or another, as well as while their operation, it is often necessary to heat them up to rather high temperatures. In this case, not only readily volatile components of the reaction mixture, but also the ferrites and cobaltites themselves can undergo thermal dissociation with the vaporization of readily volatile components. The temperature of the thermal dissociation of ferrites and cobaltites beginning can be determined by a number of experimental methods. High-temperature mass spectrometry is the most convenient method of controlling the vapor phase composition, which makes it possible to de
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