Electric and magnetic properties of lanthanum barium cobaltite

Abstract

The cubic Ba0.5La0.5CoO3‐δ was synthesized using solid state reaction. The structural properties were determined by the simultaneous refinement of Synchrotron Powder X‐ray Diffraction and Neutron Powder Diffraction data. Iodometric titration was used to examine the oxygen stoichiometry and average cobalt oxidation state. Low‐temperature magnetic studies show soft ferromagnetic character of fully oxidized material, with θP = 198(3) K and µeff = 2.11(2) µB. Electric measurements show the thermally activated nature of conductivity at low temperatures, whereas, due to the variable oxidation and spin state of cobalt, a single charge transport mechanism cannot be distinguished. Around room temperature, a wide transition from thermally activated conductivity to semi‐metallic behavior is observed. Under the inert atmosphere, the oxygen content lowers and the cation ordering takes place, leading to coexistence of two, ordered and disordered, phases. As a result of this change, thermally activated conductivity is observed also at high temperatures in inert atmosphere.

High-Temperature Structural and Electrical Properties of BaLnCo2O6 Positrodes

“…Figure 1 presents the differences between tetragonal and orthorhombic structures with different oxygen content. The obtained crystal structure of Ba Ln Co 2 O 6−δ strongly depends on oxygen stoichiometry [ 4 , 7 , 8 ], as well as synthesis procedure [ 9 ]. As the difference between the two polymorphs, resulting from the oxygen vacancy ordering, is very subtle, the structural studies require very high-quality data such as synchrotron radiation X-ray powder diffraction collected with 2D detectors.…”

“…The lattice parameter doubling along the c -axis confirms A -site cation ordering, while the double b -parameter results from oxygen vacancy ordering [ 12 ]. BPC has been reported to form both tetragonal and orthorhombic structure, strongly depending on oxygen stoichiometry [ 4 , 6 , 7 , 8 , 20 ], as well as synthesis procedure [ 21 ], but is reported to be stabilized in orthorhombic structure when oxygen non-stoichiometry (δ) is between 0.25 and 0.6 [ 14 ].…”

“…Oxygen stoichiometry and oxidation state of cobalt were determined using iodometric titration at room temperature. Experimental procedure and details can be found elsewhere [4]. Approximately 15-20 mg of sample was used in this procedure.…”

Structure and water uptake in BaLnCo2O6−δ (Ln =La, Pr, Nd, Sm, Gd, Tb and Dy)

“…Double perovskite barium lanthanide cobaltites, A I A II Co2O6-δ, where A I stands for Ba and A II for lanthanide (BLnCOs) and their derivatives are components in electrochemical and electrocatalytic devices [1][2][3][4][5][6][7][8][9]. It has been shown that these materials adopt multiple polymorphs, most commonly cubic (space group Pm3 ̅ m, no 221) [1,10], and A-site ordered tetragonal (P4/mmm no 123, double parameter along c-axis) or orthorhombic (Pmmm no 47, double parameters along band caxes) structures [1,11]. Furthermore, a variety of possible superstructures (e.g.…”

High‐Temperature Proton Conduction in LaSbO4

“…This class of materials has gathered interest over the years for their potential applications. Especially the so‐called triple conducting oxides, that is, materials with three mobile charge carriers (protons, oxygen ions, and electron/electron holes) were discovered and studied as potential electrode materials [2–5] . The increased interest led to developing highly‐efficient fuel cells [5–7] and steam electrolyzers [8] .…”