| 1. |
- Ahmed, Istaq, 1972, et al.
(author)
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Effect of co-doping on proton conductivity in perovskite oxides BaZr0.9In0.05M0.05O3−δ (M = Yb3+ or Ga3+)
- 2010
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In: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 35:12, s. 6381-6391
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Journal article (peer-reviewed)abstract
- BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) has been prepared by solid-statesynthesis route.Rietveld analysis of neutron powder diffraction data on as-prepared samples showed thatboth samples crystallise in the cubic space group Pm-3m. Scanning electron microscopyanalysis showed that the grains intheBaZr0.9In0.05Ga0.05O3-d sample were larger than the BaZr0.9In0.05Yb0.05O3-d sample. Dynamic thermogravimetric analysis indicates that the proton concentration was higher inpre-hydrated BaZr0.9In0.05Ga0.05O3-d sample (40%oftheoretical)than that of BaZr0.9In0.05Yb0.05O3-d sample (28%oftheoretical).Proton conductivity was studied on pre-hydrated samples(under both dry and wetAr atmospheres).Thebulk proton conductivities of the heating cycle of pre-hydrated BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) samples were 2.1 * 10-5 S cm-1 and 1.9 * 10-4 Scm-1 at 350C, respectively.The effect of co-doping onproton conductivity was investigatedand the results are compared with single doped systems e.g. BaZr0.9M0.1O3-d (M=Ga3+, In3+ orYb3+) samples.
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| 2. |
- Ahmed, Istaq, 1972, et al.
(author)
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Improved Proton Conductivity in Spark-Plasma Sintered Dense Ceramic BaZr0.5In0.5O3-delta
- 2010
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In: Electrochemical and Solid State Letters. - : The Electrochemical Society. - 1099-0062 .- 1944-8775. ; 13:11, s. B130-B134
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Journal article (peer-reviewed)abstract
- Spark-plasma sintering method was used to prepare dense proton conducting perovskite oxide BaZr0.5In0.5O3-delta. Analysis of X-ray powder diffraction data showed that the sample adopt the cubic crystal structure having the space group Pm3m. Thermogravimetric analysis of prehydrated samples showed significant mass losses beyond 300 degrees C due to loss of protons as water vapor. Scanning electron microscope images show that the grain size of the spark-plasma sintered dense sample was smaller than that of solid-state sintered porous sample. The highest total proton conductivity (2 X 10(-3) S cm(-1) at 450 degrees C) was found for dense spark-plasma sintered sample under wet H-2 than the samples prepared by other routes.
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| 3. |
- Ahmed, Istaq, 1972, et al.
(author)
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Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr[sub 0.5]In[sub 0.25]Yb[sub 0.25]O[sub 3 - delta]
- 2010
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In: Journal of The Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:12, s. B1819-B1824
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Journal article (peer-reviewed)abstract
- A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.5×10−4 and 2.2×10−5 S cm−1, respectively, at 300°C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200°C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.3×10−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs.
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| 4. |
- Eurenius, Karinh, 1980, et al.
(author)
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Investigation of proton conductivity in Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ pyrochlores
- 2010
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In: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 181:3-4, s. 148-153
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Journal article (peer-reviewed)abstract
- The results of the synthesis and characterisation of pyrochlore systems Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ are reported. The electrical conductivity of the materials was studied using impedance spectroscopy under wet and dry oxygen and argon. Enhancements of the bulk conductivity at temperatures up to 500 °C were observed for wet conditions indicative of significant proton conductivity. The presence of dissolved protons in the materials is supported by thermogravimetric analysis and infrared spectroscopy. Proton conduction was confirmed by measurements in O2/D2O and Ar/D2O. The results reveal the importance of the correct choice of dopant site for the pyrochlore structure, with A-site substitution yielding the highest levels of proton, as well as oxide ion, conduction. For both samples bulk, rather than grain boundary, conduction is found to be dominant.
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