Electrical Conductivity Of Sr Research Articles

The influence of Sc3+ doping on the crystal structure and electrical conductivity of Sr(Ti0.2Zr0.2Y0.2Sn0.2Hf0.2)O3-σ high-entropy perovskite oxides

High entropy materials offer optimal conditions for regulating and modifying new material properties due to their vast composition space. Through traditional solid phase sintering, this article successfully synthesized a series of Sr(Ti0.2Zr0.2Y0.2Sn0.2Hf0.2Sc0.2x)O3-σ high entropy perovskite oxides with varying Sc3+ doping concentrations and comprehensively investigated the microstructure morphology, crystal structure, and electrical conductivity of Sc-doped HEPs as well as their influence on oxygen transfer rate. The results demonstrate the successful incorporation of Sc3+ into the high entropy lattice, resulting in a transformation of the crystal to a positively cubic structure with enhanced reciprocity. While the lattice vibration of BO6 octahedron is weakened by the introduction of Sc3+, it has no impact on the phase stability of the crystal structure. Moreover, The results of the electrochemical impedance spectroscopy test demonstrate that at a temperature of 750 °C, with a doping amount of Sc3+ at 0.14, the conductivity (σ) of Sc3+ is measured to be 5.74 × 10−3 S/cm, exhibiting an increase of 61.7% compared to non-doped samples. Correspondingly, the activation energy (Ea) is reduced from 0.51 eV to 0.39 eV as well. This doping strategy effectively expands the potential applications of high entropy perovskite oxides in solid oxide fuel cells (SOFCs). These findings serve as a driving force for further investigation into high entropy ceramics of the strontium series that exhibit optimal properties.

Phase composition, densification and electrical conductivity of La0.9Sr0.1Ga0.8Mg0.2O3−δ consolidated by the two-stage sintering method

The influence of the method of sintering on densification, phase assemblage and electrical conductivity of Sr- and Mg-doped lanthanum gallate was investigated aiming to optimize the sintering process of this solid electrolyte. Powder mixtures were prepared by solid state reactions, and the sintering of green compacts was carried out by the two-stage method varying the temperature of the first stage (T1) and the isothermal temperature (T2) and time (t2) profile. The type and content of predominant impurity phases depend on specific parameters of the sintering process. In the first stage of sintering, the content of impurity phases, such as LaSrGaO4 and La4Ga2O9, decreases with increasing temperature. The relative density of sintered specimens reaches 99% whenever T1 is 1500°C. The mean grain size varies from 1.45 to 4.9µm. At 600°C the electrical conductivity attains 12mScm−1 for T1 1400°C and T2 1350°C for 5h, with activation energy of approximately 1eV.

The structural and electrical properties of Sr2Ni0.75Mg0.25MoO6 and its compatibility with solid state electrolytes

The double perovskite Sr 2 Ni 0.75 Mg 0.25 MoO 6 was evaluated as a potential anode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). Its phase stability, electrical conductivity, thermal and chemical compatibility with perspective oxygen-ionic (Zr 0.85 Y 0.15 O 2 − δ , Ce 0.8 Sm 0.2 O 2–δ , La 0.88 Sr 0.12 Ga 0.82 Mg 0.18 O 3 − δ ) and protonic (BaCe 0.8 Sm 0.2 O 3 − δ , Ba 2 In 1.67 W 0.33 O 5 + δ ) electrolytes were investigated. The Sr 2 Ni 0.75 Mg 0.25 MoO 6 sample was obtained via the combustion method at 1373 K in air. X-ray powder diffraction data and dilatometric measurement show that there is a tetragonal → cubic structure phase transition at 510 K. It was found that the total electrical conductivity of a molybdate ceramic sample strongly depends on the ambient atmosphere and changes from 0.007 S/cm (pO 2 = 0.21 atm) to 33.217 S/cm (pO 2 = 1 × 10 − 19 atm) at 1073 K, respectively. By dilatometry measurement under isothermal conditions it was established that the rapid change in conductivity is most probably connected to the partial reduction of the Mo-ions. TEC values calculated in two temperature ranges of 300–500 K and 500-1073 K were 12.3 × 10 − 6 and 13.5 × 10 − 6 K − 1 , respectively. • Sr 2 Ni 0.75 Mg 0.25 MoO 6 was synthesized and evaluated as anode materials for IT-SOFCs. • The material is redox stable. • Electrical conductivity of Sr 2 Ni 0.75 Mg 0.25 MoO 6 reaches 33.37 S·cm − 1 at 1073 K (pO 2 = 1·10 − 18 atm). • The material is chemically and thermally compatible with some IT-SOFC electrolytes.

Preparation and Electrical Conductivity of Sr(Zr<sub>1-x</sub>Al<sub>x</sub>)O<sub>3-x/2</sub> Perovskite Solid Solution (x = 0-0.5)

Perovskite solid solution of Sr(Zr1-xAlx)O3-x/2 was prepared by a coprecipitation method using corresponding aqueous solutions and ammonium carbonate solution. The freeze-dried powders at x = 0-0.5, heated at 1000°C for 4 h in air, were identified to be an orthorhombic SrZrO3 solid solution. The highest electrical conductivity of Sr(Zr1-xAlx)O3-x/2 system sintered at 1400°C was measured at x = 0.2 (3.80×10-4 S/cm at 800°C, activation energy 109 kJ/mol ). The activation energy also showed a maximum value at x = 0.25 .

Effects of manganese substitution at the B-site of lanthanum-rich strontium titanate anodes on fuel cell performance and catalytic activity

Abstract Sr 0.4 La 0.6 Ti 1− x Mn x O 3− δ with rhombohedral structure has been investigated in terms of their electrochemical performance, redox stability, and electro-catalytic properties for solid oxide fuel cell anodes. The performance of Sr 0.4 La 0.6 Ti 1− x Mn x O 3− δ anodes for solid oxide fuel cells strongly depends on the Mn substitution at the B-site of the perovskites. Electrical conductivity of Sr 0.4 La 0.6 Ti 1− x Mn x O 3− δ increases with increasing Mn content. X-ray photoelectron spectroscopy analysis reveals that the amount of Mn 3+ and Ti 3+ , which is an electronic charge carrier, increases with Mn doping. The reduced anode powders with high Mn/Ti ratio show oxygen storage capability and a low carbon deposition rate. Linear thermal expansion coefficients of Sr 0.4 La 0.6 Ti 1− x Mn x O 3− δ anodes range from 9.46×10 −6 K −1 to 11.3×10 −6 K −1 . The maximum power densities of the single cell with the Sr 0.4 La 0.6 Ti 0.2 Mn 0.8 O 3− δ anode in humidified H 2 and CH 4 at 800 °C are 0.29 W cm −2 and 0.24 W cm −2 , respectively.

Effect of Co doping on the properties of Sr 0.8Ce 0.2MnO 3− δ cathode for intermediate-temperature solid-oxide fuel cells

The effect of the Co doping on the structure, electrical conductivity and electrochemical properties of Sr 0.8Ce 0.2MnO 3− δ was investigated. The Co doping decreased the sintering temperature by about 100 °C and cubic structure was synthesized for Sr 0.8Ce 0.2Mn 0.8Co 0.2O 3− δ . The electrical conductivity of Sr 0.8Ce 0.2Mn 0.8Co 0.2O 3− δ reached 102 S cm −1 at 700 °C, which was sufficient to provide low ohmic losses at the cathode. In comparison with Sr 0.8Ce 0.2MnO 3− δ , the area-specific resistance of Sr 0.8Ce 0.2Mn 0.8Co 0.2O 3− δ was 0.10 Ω cm 2 at 750 °C, which was about 20 times lower than that of Sr 0.8Ce 0.2MnO 3− δ . While the exchange current density i 0 of Sr 0.8Ce 0.2Mn 0.8Co 0.2O 3− δ was 0.49 A cm −2 at 800 °C, that for Sr 0.8Ce 0.2MnO 3− δ was 0.11 A cm −2. The results show that the Sr 0.8Ce 0.2Mn 0.8Co 0.2O 3− δ cathode had high catalytic activity for oxygen reduction reaction in the temperature range of 700–800 °C.

The effect of Co addition on the electrical conductivity of Sr- and Mg-doped LaAlO3

Co was added to see its effect on the electrical conductivity of Sr- and Mg-doped LaAlO3 (La0.9Sr0.1 Al0.9Mg0.1O3, LSAM). Electrical conductivities of La0.9Sr0.1(Al0.9Mg0.1)1− xCoxO3 (LSAMC) for x = 0–0.20 were measured using 2-probe a.c. and 4-probe d.c. method at temperature between 300 and 1300∘C in air, and as a function of Po 2 (1–10−15 atm) at 1200∘C. Electrical conductivities in air increased with increasing Co content, while their activation energy decreased. From the impedance spectroscopy analysis, it was found that both the grain and the grain boundary conductivities of LSAMC samples increased rapidly with Co-addition. LSAMC samples were oxygen ion conductors in low Po2 and mixed conductors in high Po 2 up to x = 0.1 just like LSAM. With Co-doping, p-type conductivities increased, however, ionic conductivities remained nearly constant.

Synthesis and electrical conductivity of Sr- and Mn-substituted LaAlO 3 as a possible SOFC anode material

Single phase (La,Sr)(Al,Mn)O 3 perovskites were synthesized and their electrical conductivity was studied as a function of temperature and oxygen partial pressure. The electrical conductivity was found to increase with Mn content, temperature and oxygen partial pressure, thus (La, Sr)(Al, Mn)O 3 may be regarded as a diluted system of (La,Sr)MnO 3. The highest electrical conductivity at 810 °C in air and humidified Ar/4% H 2 was observed for (La 0.8Sr 0.2) 0.94Al 0.5Mn 0.5O 3 and reached 12 and 2.7 S/cm, respectively.

The effect of Ti addition on the electrical conductivity of Sr- and Mg-doped LaAlO 3

Ti was added into acceptor-doped LaAlO 3 to enhance the mixed electronic and ionic conductivity at low Po 2. Electrical conductivities of [La 0.9Sr 0.1Al 0.9Mg 0.1O 3] 1− x [La 2 / 3 TiO 3] x (LAT) for x = 0–0.30 were measured using 4-probe d.c. method at temperatures between 1000 and 1300 °C and as a function of oxygen partial pressure (Po 2 = 1∼10 − 15 atm) at 1200 °C. Electrical conductivities in air decreased with increasing Ti contents ( x) for 0 < x < 0.15, and increased for 0.15 < x < 0.30 after showing minimum values at x = 0.15. The activation energy in air showed percolative change near x∼0.13. LAT samples for 0 ≤ x ≤ 0.10 were oxygen ion conductors in low Po 2 and mixed (p-type and ionic) conductors in high Po 2. However, for x ≥ 0.15, n-type conductivity was dominant in low Po 2. For x ≥ 0.20, the p-type conductivity in high Po 2 disappeared and the n-type conductivity was dominant in all Po 2 range and increased with increasing Ti concentration.

Electrical conductivity of Sr and Mg doped LaAlO 3

The electrical conductivity of 10% Sr and 10% Mg doped LaAlO 3 (LSAM9191) was measured using impedance spectroscopy at temperatures between 400 and 1000 °C. Between 800 and 1000 °C, the conductivity was also measured as a function of oxygen partial pressure ( P O 2 ). Below 550 °C, the grain boundary resistance mostly determined the overall conductivity that nearly disappeared above 800 °C. In the temperature region where the sample resistance is mostly determined by grain property, LSAM9191 was an oxygen ion conductor at low P O 2 and a mixed conductor at high P O 2 . With increasing temperature, the ionic conduction region only slightly increased. Thus, LSAM9191 is a promising material as an oxygen ion conductor at high temperature in low P O 2 .

Optical absorption spectra and the nature of conduction carriers of hole-doped Sr 1+ xLa 1− xFeO 4

The optical absorption as calculated from the diffuse reflectivity in the range of 0.5–5 eV and the temperature dependence of d.c. electrical conductivity of Sr 1+ x La 1− x FeO 4 (0 ≦ x ≦ 0.3) with a K 2NiF 4 structure, were measured. The results obtained were analyzed based on the small polaron model, and discussed with reference to the changes in the physical properties and the electronic structure previously reported. The Mott type and charge-transfer type excitations were observed at ∼2.2 and ∼2.7 eV, respectively, in the optical absorption spectrum of the undoped SrLaFeO 4. An additional broad absorption band below 1 eV was observed, and its intensity was directly proportional to the d.c. electrical conductivity at room temperature. Thus the absorption band below 1 eV was assigned to the optically induced polaron hopping. Based on the small polaron theory, the hopping energies of small polarons from 0.14 to 0.24 eV were obtained. These values were close to the activation energies of d.c. electrical conductivity obtained from the σT 3 2 vs 1 T plots. The results, in which the Fermi-level was fixed in the middle of the energy band gap of the photoemission spectroscopy previously reported could not be explained by the rigid-band model, but were consistent with the small polaron model.