Effect of sintering conditions on the electrical-transport properties of the SrZrO3-based protonic ceramic electrolyser membrane

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

doi:10.1016/j.jpowsour.2016.09.075

Cited by 23 publications

(22 citation statements)

References 47 publications

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“…4(a)). The higher conductivity in wet compared to dry at high temperature, as is typical for proton-conducting oxide systems [8,25], due to decreasing proton content with increasing temperature attributable to the exothermic hydration reaction:…”

Section: Phase Analysismentioning

confidence: 99%

Electrical properties of proton-conducting BaCe0.8Y0.2O3-δ and the effects of bromine addition

2019

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A detailed analysis of the electrical properties of the proton-conducting BaCe0.8Y0.2O3- phase (BCY20) and the effects of Br doping has been undertaken. Members of the system of nominal stoichiometry BaCe0.8Y0.2O2.9-(x/2)±Brx (x = 0, 0.05, 0.1 and 0.2) were synthesised by a citrate-nitrate process and high-temperature annealing up to 1500 °C. Xray diffraction revealed the formation of single-phase material with a monoclinically distorted perovskite structure (space group I2/m) with greater distortion for Brsynthesised phase. Significant contrasts in electrical behaviour and stability between BCY20 and Br-synthesised series members were also found. However, chemical analysis by total X-ray fluorescence spectroscopy indicated that only trace amounts of Br remain after synthesis, indicating that Br addition influences stoichiometry but not directly the physicochemical properties. Higher conductivity is observed for the Br-synthesised compositions in wet and dry oxidising conditions in the temperature range 300-900°C, reaching a value of 5.8 S•m -1 at 800 ºC for the x = 0.2 member in wet O2 (pH2O ~ 0.022 atm). Determination of partial-conductivity components indicated that, in humid conditions and low temperature, conductivity of 20% Br-synthesised material is principally protonic (tH = 0.91 at 600 °C and pO2 = 0.2 atm) and superior to that of BCY20. Mixed oxide-ionic-electronic conductivity dominates at high pO2 (1 atm) and oxide-ionic conductivity at low pO2 (~ 10 -4 atm) in the temperature range 600-900 ºC for both BCY and Br-doped samples. Stability was found to be poorer in CO2 for the Brsynthesised phases as determined by thermogravimetry and prolonged conductivity measurements.

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Section: Phase Analysismentioning

confidence: 99%

Electrical properties of proton-conducting BaCe0.8Y0.2O3-δ and the effects of bromine addition

2019

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“…For illustration, the temperature dependences of the total, oxygen-ion and electron-hole conductivities of SZY in air (pO 2 ≈ 21 kPa) calculated with the help of Equations (7)- (12) are shown in Figure 8. For comparison, the total conductivity of the bulk SZY sample in air obtained from the impedance measurements and the conductivity of a bulk sample of SrZr 0.9 Y 0.1 O 3−δ measured in wet oxidizing conditions (wet oxygen, pH 2 O ≈ 3000 Pa) reported in [42] are also presented in Figure 8. It can be seen that the calculated and measured values of conductivity are in good agreement.…”

Section: Conductivity and Transport Numbers Of Oxygen Ions As Functiomentioning

confidence: 99%

“…Figure 8. For comparison, the total conductivity of the bulk SZY sample in air obtained from the impedance measurements and the conductivity of a bulk sample of SrZr0.9Y0.1O3−δ measured in wet oxidizing conditions (wet oxygen, pH2O ≈ 3000 Pa) reported in [42] are also presented in Figure 8. It can be seen that the calculated and measured values of conductivity are in good agreement.…”

Section: Conductivity and Transport Numbers Of Oxygen Ions As Functiomentioning

confidence: 99%

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Transport Properties of Film and Bulk Sr0.98Zr0.95Y0.05O3−δ Membranes

2020

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In electrode-supported solid oxide fuel cells (SOFCs) with a thin electrolyte, the electrolyte performance can be affected by its interaction with the electrode, therefore, it is particularly important to study the charge transport properties of thin electrode-supported electrolytes. The transport numbers of charged species in Ni-cermet supported Sr0.98Zr0.95Y0.05O3−δ (SZY) membranes were studied and compared to those of the bulk membrane. SZY films of 2.5 μm thickness were fabricated by the chemical solution deposition technique. It was shown that the surface layer of the films contained 1.5–2 at.% Ni due to Ni diffusion from the substrate. The Ni-cermet supported 2.5 μm-thick membrane operating in the fuel cell mode was found to possess the effective transport number of oxygen ions of 0.97 at 550 °C, close to that for the bulk SZY membrane (0.99). The high ionic transport numbers indicate that diffusional interaction between SZY films and Ni-cermet supporting electrodes does not entail electrolyte degradation. The relationship between SZY conductivity and oxygen partial pressure was derived from the data on effective conductivity and ionic transport numbers for the membrane operating under two different oxygen partial pressure gradients—in air/argon and air/hydrogen concentration cells.

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“…Moreover, since the UV-PYS measurement under atmospheric condition is applicable only to materials with small ionization energy (E i ) of less than 7 eV because oxygen molecules in the atmosphere show strong UV absorption in the higher photon energy (hν) region than 7 eV, we employed the UV-PYS measurement under vacuum condition to evaluate E i of the proton-conducting oxides with the deep VBM and large E i . We focused on the electronic structures of proton-conducting solid-solution perovskite oxide between BaZr 0.8 Y 0.2 O 3−δ (BZY) and SrZr 0.95 Y 0.05 O 3−δ (SZY) expressed as (1−x)BZY-xSZY (BSZY) as model materials [25][26][27] because partial substitution of A site of the Ba-based perovskites with high protonic conductivity for Sr can improve its chemical stability under humidified atmosphere, sinterability, and phase homogenity. 28,29 Since the interactions of the defects are reflected in the electronic structure and also the electronic structure dominates the electron/hole concentration, clarification of the absolute energy levels of VBM, CBM, and defect state in BSZY solid solution can be a stepping stone to understand the transport property of this system from the viewpoint of the electronic structure.…”

Section: Introductionmentioning

confidence: 99%

Experimental analyses for electronic structure of barium zirconate‐strontium zirconate proton‐conducting solid solution

2021

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In proton-conducting oxides, analyses for their electronic structure contribute to the understanding of interactions between defects in them. In this study, electronic band alignment of (1−x)BaZr 0.8 Y 0.2 O 3−δ (BZY)-xSrZr 0.95 Y 0.05 O 3−δ (SZY) protonconducting solid-solution system (BSZY) which has high defect concentration and the deep valence band is experimentally investigated. By using thin-film specimens for optical absorption measurements, absorption edges derived from electron transition from the valence band to the conduction band which was insensitive to the proton incorporation were clearly observed in spite of the high defect concentration.The obtained optical band gap energy increased from 5.61 to 5.89 eV with increasingx, which was consistent with a composition dependence of Zr(Y)O 6 octahedral tilting. Ultraviolet photon-yield spectroscopy (UV-PYS) measurements under vacuum condition revealed that BZY and SZY had ionization energy of 6.98 and 7.31 eV, respectively, and thus the absolute energy levels of the valence band maximum and the conduction band minimum of BSZY were experimentally clarified. We propose that the combination of the optical absorption measurements using thin-film specimens and the UV-PYS measurements under vacuum condition is effective in evaluating fundamental electronic structures of proton-conducting oxides.

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Effect of sintering conditions on the electrical-transport properties of the SrZrO3-based protonic ceramic electrolyser membrane

Cited by 23 publications

References 47 publications

Electrical properties of proton-conducting BaCe0.8Y0.2O3-δ and the effects of bromine addition

Electrical properties of proton-conducting BaCe0.8Y0.2O3-δ and the effects of bromine addition

Transport Properties of Film and Bulk Sr0.98Zr0.95Y0.05O3−δ Membranes

Experimental analyses for electronic structure of barium zirconate‐strontium zirconate proton‐conducting solid solution

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