Thermodynamics of Formation and Disordering of YBaCo2O6-δ Double Perovskite as a Base for Novel Dense Ceramic Membrane Materials

Abstract

Differential scanning calorimetry studies of the complex oxide YBaCo2O6-δ (YBC), combined with the literature data, allowed outlining the phase behavior of YBC depending on the oxygen content and temperature between 298 K and 773 K. The oxygen nonstoichiometry of single-phase tetragonal YBC was measured at different temperatures and oxygen partial pressures by both thermogravimetric and flow reactor methods. The defect structure of YBC was analyzed. As a result, the thermodynamic functions (, ) of the defect reactions in YBC were determined. Experimental data on the oxygen content and those calculated based on the theoretical model were shown to be in good agreement. Standard enthalpies of formation at 298.15 K () were obtained for YBC depending on its oxygen content using solution calorimetry. It was found that = f(6-δ) function is linear in the range of (6-δ) from 5.018 to 5.406 and that its slope is close to the value of the enthalpy of the quasichemical reaction describing oxygen exchange between the oxide and ambient atmosphere, which confirms the reliability of the suggested defect structure model.

Advancements in Perovskite‐Based Cathode Materials for Solid Oxide Fuel Cells: A Comprehensive Review

“…[145] Although YBaCo 2 O 5 + δ and HoBaCo 2 O 5 + δ are susceptible to decomposing in air at high temperatures, they have gained attention due to their lower TEC values. [146][147][148] Nevertheless, stability can be achieved through controlled and selective doping strategies. Additionally, research demonstrated that replacing ions with smaller alkali ions at the Ba 2 + site could greatly improve the electrochemical performance, leading to a significant alteration in oxygen non-stoichiometry.…”

Progress in Developing LnBaCo2O5+δ as an Oxygen Reduction Catalyst for Solid Oxide Fuel Cells

“…Over the past few years, owing to its unique crystal structure, considerable efforts have been directed towards investigating the MIEC double perovskite oxides LnBaCo 2 O 5+δ (Ln = Lanthanide). These materials find potential applications across a multitude of domains, such as magnetism [15][16][17], SOFCs, proton-conductive ceramic fuel cells [18][19][20][21][22][23][24][25], water electrolysis [26][27][28], CO 2 electrolysis [29], chemical sensors [30][31][32], ceramic semi-permeable membranes [33][34][35], metal-air batteries [36,37], soot combustion [38], supercapacitors [39], photocatalysis [40], and solar-driven thermal storage [41,42]. Given the diverse requirements in terms of physicochemical properties for each application, this article will exclusively focus on novel strategies employed in advancing double perovskites for use as cathode catalysts in SOFCs.…”

Phase Behavior and Defect Structure of HoBaCo2O6-δ

“…Oxygen nonstoichiometry was shown to affect various properties of REBaCo 2 O 6-δ , including magnetic properties [27], temperatures of phase transitions and thermodynamic properties [27,28], and electronic and oxide ion transport [29]. It is of great importance to highlight that the oxygen content of an oxide material, being measured reliably depending on temperature (T) and oxygen partial pressure (pO 2 ), enables validating its defect structure model and, consequently, evaluating the thermodynamics of defect interactions.…”

“…The Y-containing double perovskite cobaltite, YBC, was shown [28] to undergo two structural transitions upon increasing temperature: the first tetragonal (P4/mmm, 332-type superstructure) phase transforms to an orthorhombic (Pmmm and 122-type superstructure) one and then to a tetragonal phase (P4/mmm, 112-type superstructure). The former transition occurs due to the change of the ordering pattern of oxygen vacancies and the latter because of complete disordering of oxygen vacancies.…”

“…Oxygen nonstoichiometry of REBaCo 2 O 6-δ was studied for the oxides containing the following rare-earth elements: La [33], Pr [29], Nd [34], Sm [35], Eu [35], and Gd [36]. Several methods were employed in the previous works to measure the oxygen nonstoichiometry of YBC: coulometric titration at high temperatures, 1173-1323 K [37], and thermogravimetry and flow reactor method at moderate temperatures, 573-773 K [28]. The results of the latter were used to make the proposed defect structure model [38] applicable not only in the relatively narrow range of high temperatures (1173-1323 K), but also at lower temperatures, down to 573 K. It was found that the re-evaluated enthalpies and entropies of defect interactions in YBC are close to those for GdBaCo 2 O 6-δ , being distinctively different from those for the other REBaCo 2 O 6-δ with larger rare-earth ions [28].…”