Electrical conductivity and defect chemistry of $$ {\hbox{B}}{{\hbox{a}}_x}{\hbox{S}}{{\hbox{r}}_{{1} - x}}{\hbox{C}}{{\hbox{o}}_y}{\hbox{F}}{{\hbox{e}}_{{1} - y}}{{\hbox{O}}_{{3} - \delta }} $$ perovskites

Abstract

Bulk Ba x Sr 1Àx Co y Fe 1Ày O 3Àd compositions (BSCF) were synthesized by the solid-state reaction method. The electrical conductivity of ceramic bars was measured using a dc four-probe method as a function of temperature in air up to 970°C. All compositions showed thermally activated p-type semi-conductivity up to~450°C and then a transition to metal-like conductivity. The smallpolaron hopping p-type semi-conductivity depends on the oxygen nonstoichiometry, which increases with increasing temperature. Metal-like conductivity is attributed to the overlap of the transition metal d-electron orbitals with the oxygen p-orbitals. Strontium-rich compositions show higher conductivity. The Co/Fe ratio does not influence much the p-type semi-conduction. Iron-rich compositions revealed more metal-like conduction behavior. The degree of overlap between transition metal d-orbitals and oxygen p-orbitals depends on the Ba/Sr as well as on the Co/Fe ratios.

Electrical Conductivity of Ba0.5Sr0.5Co0.8Fe0.2O3−δunder Uniaxial Compression at Elevated Temperatures

“…16 Four platinum electrodes were applied onto the surface of the specimen for the conductivity measurement. 7,19,20 The measured conductivities during heating and cooling are inconsistent at the elevated temperature, as reported in the literatures, 20 which indicates that the equilibrium state in BSCF can be only reached very slowly. Uniaxial compressive load was then gradually applied up to 350-700 N (i.e., 50-110 MPa), followed by a gradual unloading.…”

Tuning the Co Oxidation State in Ba0.5Sr0.5Co0.8Fe0.2O3-δ by Flame Spray Synthesis Towards High Oxygen Evolution Reaction Activity

“…The reason for this connection between Co oxidation state in BSCF and its OER activity lies in the concentration of oxygen vacancies [8]. BSCF [40][41][42][43][44][45][46] or perovskite-type oxides in general [47][48][49][50] have a great ability to accommodate oxygen vacancies. The occurrence of oxygen vacancies in a perovskite-type oxide requires at least one of the two charge compensation possibilities on the A-and B-site cations.…”

Reduced impedance in dual substituted strontium cobaltite nanoparticles for renewable energy applications

“…Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) is a good example of perovskite-based compound. This compound has gained interest among researchers as an effective cathode material in IT-SOFCs applications due to its excellent characteristics for intermediate temperature [5,[11][12][13][14]. However industrial applicability of BSCF is so far limited due to it's chemically instability [15,16] and reactivity towards carbon dioxide gas [17].…”

“…However industrial applicability of BSCF is so far limited due to it's chemically instability [15,16] and reactivity towards carbon dioxide gas [17]. Nonetheless, BSCF is still an admirable material due to its high conductivity, catalytic activity and outstanding oxygen transport properties which make it excellent cathode material in IT-SOFCs applications [13,14,[18][19][20]. Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) was the best reported composition so far, synthesized by sol-gel technique.…”

“…Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) was the best reported composition so far, synthesized by sol-gel technique. In the literature, different routes have been adopted so far to synthesize BSCF cathode material such as solid-state reaction route [13,14,[21][22][23], EDTA complexing method [22,24,25] etc. Beside these synthesis methods, wet chemical methods have good control on complex composition synthesis and good chemical homogeneity of the final product [26][27][28][29][30][31].…”