Ionic conductivity, structural and thermal properties of Ca2+ doped Y2Ti2O7 pyrochlores for SOFC

Gill, Jasmeet Kaur; Pandey, O.P.; Singh, K.

doi:10.1016/j.ijhydene.2011.04.216

Cited by 38 publications

(8 citation statements)

References 18 publications

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“…The Ca–O peak around 300–400 cm –1 is not observed in the band. The presence of a band around 2350 cm –1 in the YCGO sample can be attributed to the Ca–O bond . The peak around 870 cm –1 present in the YSGO sample is assigned to the Sr–O bond, and the kink around 860 cm –1 is assigned to the Ba–O bond …”

Section: Resultsmentioning

confidence: 93%

Signature of Oxide-Ion Conduction in Alkaline-Earth-Metal-Doped Y₃GaO₆

et al. 2020

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We have studied alkaline-earth-metal-doped Y 3 GaO 6 as a new family of oxide-ion conductor. Solid solutions of Y 3 GaO 6 and 2% −Ca 2+ -, −Sr 2+ -, and −Ba 2+ -doped Y 3 GaO 6 , i.e., Y (3−0.06) M 0.06 GaO 6−δ (M = Ca 2+ , Sr 2+ , and Ba 2+ ), were prepared via a conventional solid-state reaction route. X-ray Rietveld refined diffractograms of all the compositions showed the formation of an orthorhombic structure having the Cmc2 1 space group. Scanning electron microscopy (SEM) images revealed that the substitution of alkaline-earth metal ions promotes grain growth. Aliovalent doping of Ca 2+ , Sr 2+ , and Ba 2+ enhanced the conductivity by increasing the oxygen vacancy concentration. However, among all of the studied dopants, 2% Ca 2+ -doped Y 3 GaO 6 was found to be more effective in increasing the ionic conductivity as ionic radii mismatch is minimum for Y 3+ /Ca 2+ . The total conductivity of 2% Ca-doped Y 3 GaO 6 composition calculated using the complex impedance plot was found to be ∼0.14 × 10 −3 S cm −1 at 700 °C, which is comparable to many other reported solid electrolytes at the same temperature, making it a potential candidate for future electrolyte material for solid oxide fuel cells (SOFCs). Total electrical conductivity measurement as a function of oxygen partial pressure suggests dominating oxide-ion conduction in a wide range of oxygen partial pressure (ca. 10 −20 −10 −4 atm). The oxygen-ion transport is attributed to the presence of oxygen vacancies that arise from doping and conducting oxide-ion layers of one, two-, or three-dimensional channels within the crystal structure. The oxide-ion migration pathways were analyzed by the bond valence site energy (BVSE)-based approach. Photoluminescence analysis, dilatometry, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy studies were also performed to verify the experimental findings.

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Section: Resultsmentioning

confidence: 93%

Signature of Oxide-Ion Conduction in Alkaline-Earth-Metal-Doped Y₃GaO₆

et al. 2020

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“…The conductivity plots of the sample also show prominent transition after 600 °C. These transitions can be associated with the higher oxygen vacancy content in the sample at high temperatures [34]. The conductivities obtained previously for the pyrochlore structured Er 2 Ti 2 O 7 at 1000 °C is 1.3•10 -2 S•cm -1 [35].…”

Section: Resultsmentioning

confidence: 67%

Ionic conduction properties of nanocrystalline Er2Ti2O7 functional material

Sandeep¹

2020

Semicond. phys. quantum electron. and optoelectron.

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The rare-earth titanate Er 2 Ti 2 O 7 nanoceramic prepared by the modified combustion technique exhibits cubic pyrochlore structure with the space group m Fd3. Powder XRD and vibrational spectroscopic tools have been used for structural identification and confirmation. The detailed optical and photoluminescence (PL) properties of the sample have been analyzed using UV-Vis diffuse reflectance spectroscopy and PL spectroscopy. Impedance spectroscopic studies have revealed that the material exhibits conduction by hopping of ions, which increases with temperature. Z-View software has been used to fit the impedance data and deduce the electrical parameters of the samples from the equivalent circuit. The grain activation energy is less than that of grain boundary, which implies that grain conduction is predominant in the sample. The optical and electrical studies confirm that the material is a possible candidate to fabricate optical devices and construct solid oxide fuel cells.

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“…14 Moreover in pyrochlores, cation or anion disorder may give rise to order-disorder transitions inuencing also the conductivity and the presence of metal-insulator transitions. 7,[15][16][17] This phenomenon is coherent with the pyrochlores predisposition towards full or partial disorder, structural distortion and phase transition from pyrochlore to a defect uorite structure. 6,18 In this general framework, doping Y 2 Ru 2 O 7 with Zn 2+ results in mixed charge at both A and B cationic sites and consequently a ruthenium mixed valence 4+/5+ is present.…”

Section: Introductionmentioning

confidence: 64%

“…5,9 On the other hand, in the case of Y 2Àx Ca x Ru 2 O 7 it has been shown that the substitution of Y 3+ by the larger Ca 2+ signicantly inuences both the magnetic and the conductive properties. 15 At present, there is not an exhaustive view of the effective role of the A site doping since this depends on the chemical nature, valence and occupancy of dopants, and on their ionic radius, magnetic conguration and stereochemical impact. In a recent EXAFS experiment on the related undoped compound Y 2 Ru 2 O 7 , 6 we found evidence of: (i) a large magnetoelastic coupling pointed out by a huge and broad peak in the Debye-Waller factor s 2 for the Ru-O(1) rst coordination shell in the temperature region around the antiferromagnetic transition at T N x 77 K; (ii) an axial distortion of the RuO(1) 6 octahedra above a critical temperature T* x 150 K which was attributed to a precursor order-disorder (OD) transition.…”

Section: Introductionmentioning

confidence: 99%