Rate-Determining Steps of Oxygen Surface Exchange Kinetics on Sr2Fe1.5Mo0.5O6−δ

Abstract

The oxygen surface kinetics of Sr2Fe1.5Mo0.5O6−δ was determined using the 16O2/18O2 isotope exchange method with gas phase analysis at 600–800 °C. The heterogeneous exchange rates (rH) and the oxygen diffusion coefficients (D) were calculated by processing the concentration dependences of the 18O fraction using Ezin’s model. The rates of oxygen dissociative adsorption (ra) and incorporation (ri) were calculated based on a model using the three exchange type rates. It has been established that the rates ra and ri were comparable in this temperature range. Assumptions were made about the effect of the chemical composition of the surface on the rate of oxygen adsorption. It was found that the oxygen exchange coefficient (k) of Sr2Fe1.5Mo0.5O6−δ is comparable to that of La0.6Sr0.4MnO3±δ oxide. High values of the oxygen diffusion coefficient were found for Sr2Fe1.5Mo0.5O6−δ. The values were comparable to those of the double cobaltite praseodymium-barium and exceed by more than an order those of lanthanum-strontium manganite.

Positron Annihilation Lifetime Spectroscopy Insight on Free Volume Conversion of Nanostructured MgAl2O4 Ceramics

“…Results obtained by PALS can serve as a research background for the development of independent methods of diagnosing nanosized free volumes in ceramic materials, including neutron and heavy-ion irradiated MgAl 2 O 4 spinels [53][54][55], Si 3 N 4 [56], Ge 3 N 4 [57], and AlN [58][59][60] (which are especially promising as diagnostic materials for EUROfusion applications) and also facilitate understanding of porosity, development, and transformation of pores in electrochemical and other devices for energy conversion [61][62][63][64][65][66][67][68].…”

Evolution of Free Volumes in Polycrystalline BaGa2O4 Ceramics Doped with Eu3+ Ions

“…Results obtained by PAL spectroscopy can serve as a research base for the development of independent complementary methods for studying nanosized free volumes in ceramic materials, including neutron and heavy ion irradiated MgAl 2 O 4 spinels [22,27,48], Si 3 N 4 [49], Ge 3 N 4 [50] and AlN [51][52][53], which are especially promising as diagnostic materials for nuclear applications. Other interesting and very important areas are the understanding of porosity, its development and transformation in electrochemical and other devices for energy conversion [54][55][56][57][58][59][60][61][62][63][64].…”

Solid oxide electrolysis cells – current material development and industrial application

“…175 Diffusion coefficient D * (5.0 × 10 −6 cm 2 s −1 , 750 °C) and surface exchange coefficient k * (2.8 × 10 −5 cm s −1 , 750 °C) for SFM were determined to be in line with the diffusion properties of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF), 176 corresponding to La 0.6 Sr 0.4 MnO 3+ δ . 175 However, these values for the high-performance oxygen electrode material La 0.6 Sr 0.4 CoO 3 are slightly higher than reported for SFM. 177 The exchange current density of Sr 2 Fe 1.5 Mo 0.5 O 6− δ in air (0.186 A cm −2 ) 87 is higher than that of LSM (0.003–0.004 A cm −2 ) 177,178 at 800 °C and comparable to the Co-based materials (0.005–0.519 A cm −2 ).…”