SrTiO3 as a prototype of a mixed conductor Conductivities, oxygen diffusion and boundary effects

Noll, Frank; Münch, W.; Denk, I.; Maier, Joachim

doi:10.1016/0167-2738(96)00155-5

Cited by 59 publications

(44 citation statements)

References 8 publications

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“…Higher magnesium concentrations were not possible, with full reaction not occurring after five days firing at 1450 ~ From unit cell data the solubility limit of magnesium on the B site is predicted to lie between 5 -7 %. Using AC impedance spectroscopy the magnesium doped compound exhibited increased conductivity and reduced activation energy for conduction as compared to the undoped compound that would be expected from equations (1) and (2). Conductivity vs. pO2 measurements confirmed the increased p-type behaviour of the system due to doping at high oxygen partial pressures.…”

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confidence: 66%

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B site doped strontium titanate as a potential SOFC substrate

McColm

Irvine

2001

Ionics

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Abstract. Excellent thermal and mechanical stability coupled with low cost have attracted interest in the application of the cubic perovskite SrTiO~ as a substrate material in supported SOFC designs. For such designs increased substrate conductivity is beneficial. A method of improving conductivity is by cation substitution. Due to the constraint of electro-neutrality, oxygen ion vacancies can be generated in strontium titanate by successful substitution of tetra-valent titanium ions with divalent metal ions (M) to produce materials of stoichiometry SrTi~, ~,M~O,3~. By raising the intrinsic oxygen vacancy concentration in this manner there is an increase in available hopping sites. The increase in vacant sites facilitates oxygen transport through the crystal hence increases the potential for oxide ion conductivity. The synthesis of such materials was carried out by standard solid-state techniques using calcium and magnesium as dopants. B site solubility limits for both species were obtained by powder X-ray diffraction. The conductivity behaviour of successful phase pure compounds was investigated using AC impedancc spectroscopy and four point DC measurements across a range of pO., values. The B site solubility limit for magnesium was found to lie between 5 and 7 %. SrTi,~sMg~r,5029s exhibited increased conductivity and a~ducoJ activation energy for conduction as compared to undopcd strontium titanate. DC measurements lbr the same material confirmed the increased p-type behaviour of the system associated with magnesium doping at high oxygen partial pressures. IntroductionSolid oxide l~hcl cells (SOFCs) are currently at the forefront of research into new generations of energy conversion systems owing to their high efficiency, versatility and environmentally friendly nature. Considerable attention has been focused on these systems, particularly on the electrode front, where materials with improved propcrties are being sought. This study is part of a more general goal to develop new anode materials and designs which negate the problems associated with the current Ni/YSZ cermet anode; notably sintering of Ni at operating temperatures, and coking and sulphur poisoning when using natural gas as fuel [1 ].Perovskites oxide materials possess general stoichiomerry ABO~. Conventionally the A cation is larger than the B cation. In the archetype the A cation has an oxidation state of +2 and the B cation has oxidation state +4. These materials comprised of 3 different ionic species,

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confidence: 66%

“…(1) and (2). It is worth noting that at high pO2 any enhanced ionic conductivity achieved by lattice oxygen vacancy creation is essentially removed at …”

Section: Po 2 Measurementsmentioning

confidence: 99%

B site doped strontium titanate as a potential SOFC substrate

McColm

Irvine

2001

Ionics

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“…Acceptor segregation to the grain boundary region is expected if donor-type interface charges exist at the sintering temperatures (ϳ1600 K), and such segregation has been observed in both Ni-doped and Fe-doped SrTiO 3 ceramics. 15,16 Unless otherwise stated, an equilibrium solute segregation coefficient kЈ ϭ C A Ti (0)/C A Ti (ϱ) ϭ 5 is assumed herein, and C A Ti (x) is assumed to decay exponentially from its grain boundary value to the bulk value, C A Ti (ϱ), over a distance of ϳ5 nm, in keeping with reported high-resolution energy dispersive spectroscopy results. 15,16 The solute conservation condition for acceptors with a single ionization state…”

Section: Calculation Of Defect Distributionsmentioning

confidence: 96%

Equilibrium Point Defect and Electronic Carrier Distributions near Interfaces in Acceptor‐Doped Strontium Titanate

McIntyre

2000

Journal of the American Ceramic Society

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A mathematical model based on Frenkel's theory for charged defect segregation at interfaces is used to calculate the equilibrium grain boundary depletion layer widths and conductivity profiles in acceptor-doped SrTiO 3 ceramics. The calculations examine the effect of oxygen vacancy equilibration during annealing at moderate temperatures (ϳ1000 K) on the development of interfacial charge that influences grain boundary electrical properties at lower temperatures. Good agreement is demonstrated between the model predictions and experimental results reported in the literature.

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“…However, also in oxides with applications relying on a high insulation resistance at room temperature, mixed conductivity might become relevant either at high temperatures or upon high field load. [3][4][5][6][7][8] Examples for such materials are lead zirconate titanate (PZT) in actuators or BaTiO 3 in capacitors.…”

Section: Introductionmentioning

confidence: 99%

“…via In the case of dilute ionic as well as electronic defects, chemical potentials of all defects d can be expressed as (7) with normalized defect concentrations (8) In Eq. (7) μ d 0 is the standard chemical potential of the defect.…”

Section: Introductionmentioning

confidence: 99%

The Chemical Capacitance as a Fingerprint of Defect Chemistry in Mixed Conducting Oxides

Schmid¹,

Rupp

Slouka

et al. 2016

ACSi

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The oxygen stoichiometry of mixed conducting oxides depends on the oxygen chemical potential and thus on the oxygen partial pressure in the gas phase. Also voltages may change the local oxygen stoichiometry and the amount to which such changes take place is quantified by the chemical capacitance of the sample. Impedance spectroscopy can be used to probe this chemical capacitance. Impedance measurements on different oxides ((La,Sr)FeO 3-δ = LSF, Sr(Ti,Fe)O 3-δ = STF, and Pb(Zr,Ti)O 3 = PZT) are presented, and demonstrate how the chemical capacitance may affect impedance spectra in different types of electrochemical cells. A quantitative analysis of the spectra is based on generalized equivalent circuits developed for mixed conducting oxides by J. Jamnik and J. Maier. It is discussed how defect chemical information can be deduced from the chemical capacitance.

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SrTiO3 as a prototype of a mixed conductor Conductivities, oxygen diffusion and boundary effects

Cited by 59 publications

References 8 publications

B site doped strontium titanate as a potential SOFC substrate

B site doped strontium titanate as a potential SOFC substrate

Equilibrium Point Defect and Electronic Carrier Distributions near Interfaces in Acceptor‐Doped Strontium Titanate

The Chemical Capacitance as a Fingerprint of Defect Chemistry in Mixed Conducting Oxides

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