New Oxygen-Deficient Perovskite La(Al 0.5 Zn 0.5 )O 2.75 : Synthesis, Structure, and Transport Properties
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HE 100th ANNIVERSARY OF URAL FEDERAL UNIVERSITY
New Oxygen-Deficient Perovskite La(Al0.5Zn0.5)O2.75: Synthesis, Structure, and Transport Properties A. V. Egorovaa,b, K. G. Belovaa,b, and I. E. Animitsaa,b,* a
Yeltsin Ural Federal University, Yekaterinburg, 620002 Russia Institute of High Temperature Electrochemistry, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620219 Russia *e-mail: [email protected]
b
Received March 3, 2020; revised March 25, 2020; accepted April 14, 2020
Abstract—The solid-phase synthesis of oxygen-deficient perovskite La(Al0.5Zn0.5)O2.75 is performed for the first time. The perovskite crystallizes in space group Pm3m with a lattice parameter of 3.7932 Å. The cationic composition of the phase is confirmed via chemical analysis. It is shown that lanthanum alumina zincate has a mixed type of conductivity in the region of high oxygen partial pressures and temperatures above 500°C, while oxygen-ion transport predominates at temperatures below 400°C. Introducing zinc into the B-sublattice of perovskite allows high-density ceramics (>95%) to be obtained. Keywords: perovskite, lanthanum alumina zinc, structure, conductivity DOI: 10.1134/S0036024420120092
INTRODUCTION Oxide compounds that crystallize in the ABO3 perovskite structure are the most intensely studied materials in chemistry and solid state physics [1]. On the one hand, interest in perovskites is due to their important physicochemical properties: ferroelectric, antiferroelectric, ferromagnetic, and ferroelastic [2, 3]. Perovskites also exhibit catalytic [6] and semiconductor properties, superconductivity [4], and ionic conductivity [5]. The possibility of combining sets of physicochemical characteristics determines the high fundamental importance of perovskites as a special class of inorganic compounds. On the other hand, the tolerance of the perovskite structure allows to obtain a wide range of compounds using different ways of modifying the structure. We can therefore deliberately fit a property of practical importance and greatly expand the boundaries of the search for new compounds with certain functional properties. To create new ceramic materials with structurally sensitive properties, it is important to identify a specific defect. Of particular interest are perovskites with oxygen deficiency. Such compounds are capable of fast oxygen-ion transport and, depending on the ratio of ionic and electronic conductivity, can be used in such electrochemical devices as electrolytes, membrane materials, and cathodes. The main problem with using such materials is their low chemical resistance to acidic gases, particularly CO2. The
chemical stability of a substance depends directly on its elemental composition. For example, the presence of an alkaline earth component in the composition of perovskites A+2B+4O3 can result in the formation of the corresponding carbonates [7–9], and thus to the destruction of the material. A promising area of material science research is therefore developing new oxygen-deficient compounds that do n
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