High-Temperature Structural and Electrical Properties of BaLnCo2O6 Positrodes

Abstract

The application of double perovskite cobaltites BaLnCo2O6−δ (Ln = lanthanide element) in electrochemical devices for energy conversion requires control of their properties at operating conditions. This work presents a study of a series of BaLnCo2O6−δ (Ln = La, Pr, Nd) with a focus on the evolution of structural and electrical properties with temperature. Symmetry, oxygen non-stoichiometry, and cobalt valence state have been examined by means of Synchrotron Radiation Powder X-ray Diffraction (SR-PXD), thermogravimetry (TG), and X-ray Absorption Spectroscopy (XAS). The results indicate that all three compositions maintain mainly orthorhombic structure from RT to 1000 °C. Chemical expansion from Co reduction and formation of oxygen vacancies is observed and characterized above 350 °C. Following XAS experiments, the high spin of Co was ascertained in the whole range of temperatures for BLC, BPC, and BNC.

Chemical lattice strain in nonstoichiometric oxides: an overview

“…148 and 149, but from the temperature dependences of unit cell parameters by subtracting the low-temperature linear trend from the total ε values assuming temperature-independent TEC. In this respect, the volumetric chemical expansion of NdBaCo 2 O 6– δ determined in a similar manner by Cherepanov et al 248 from the dilatometric experiments coincides with that measured by Szpunar et al , 234 but is visibly greater than that found by Cox-Galhotra et al 148 (see Fig. S4 in the ESI†).…”

“…8, where the measurement results at similar temperatures are presented for RBaCo 2 O 6– δ (R = Pr, Nd, Gd), β a ≈ − β c for these double perovskite cobaltites, and their chemical expansion is close, taking into account the scatter in the data. 123,148,149 However, when all available experimental data for each of these oxides are considered, 31,123,144,148,149,233–235 it is immediately seen (Fig. S1–S3 in the ESI†) that the ε chem ( δ ) values do not often coincide well except for GdBaCo 2 O 6– δ , for which the results of Mogni et al , 233 Tsvetkov et al 123 and Chatterjee et al 31 agree with each other in the overlapping δ ranges.…”

“…81 One clear exception is LaBaCo 2 O 6– δ , 236–238 for which both expansion of a and contraction of c are higher than for the other RBaCo 2 O 6– δ (R = Pr, Nd, Gd). 31,123,144,148,149,233–235 Bernuy-Lopez et al 236 even claimed the expansion of LaBaCo 2 O 6– δ along the c axis, but their data are inconsistent across the plots presented in the article, and neither their nonstoichiometry values nor crystallographic data are supported by other studies. 243–245…”

Microstructural Design of Ba0.5La0.5Co0.5Fe0.5O3 Perovskite Ceramics

“…The positrode performance is what limits current electrochemical devices based on PCCs and much effort was put into their development [ 10 , 11 , 12 , 13 ]. Recently, we have focused on the group of BaLnCo 2 O 6 (Ln—a lanthanide) perovskite compounds that showed promising properties for application as positrodes [ 14 , 15 , 16 ]. This system exhibits high electrical conductivity in a wide temperature range.…”

Special Issue: Thermal Analysis of Materials

“…Another set of papers deals with the development of new or application-specific approaches, namely laser interferometry techniques for high precision measurements on non-standard samples, such as composite truss structures [ 5 ]; measurements of high temperature compressive creep in spark plasma sintering apparatuses [ 6 ]; measurements of the density of liquid oxides with aero-acoustic levitators [ 7 ]; and the simultaneous estimation of thermal conductivity and heat capacity in metal alloys [ 8 ].The range of materials covered includes polymers [ 9 , 10 ]; natural complex inorganic materials, such as natural sorbents [ 1 ] and industrial-grade thermal insulation [ 4 ]; single phase ceramic materials, such as spinel MgAl 2 O 4 [ 11 ], rare earth sesquioxides [ 12 ], and double perovskite cobaltites [ 13 ]; metals, alloys, and intermetallic compounds [ 8 , 14 , 15 , 16 ].…”