Order-Disorder Transitions in Gadolinium Zirconate: A Potential Electrolyte Material in Solid Oxide Fuel Cells

1995 ◽  
Vol 393 ◽  
Author(s):  
Scott Meilicke ◽  
Sossina Haile
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Transition Temperature ◽  
Ionic Conductivity ◽  
Solid Oxide Fuel Cells ◽  
Low Temperatures ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Gadolinium Zirconate ◽  
X Ray

ABSTRACTRare-earth, yttrium, and calcium doped zirconates are the materials of choice for electrolytes in solid oxide fuel cells. The dopant in these materials serves not only to stabilized the cubic phase of zirconia, but also to introduce anion defects that presumably increase the ionic conductivity. In order to understand the relationships between anion defect distribution, thermal history and ionic conductivity, the structural properties of gadolinium zirconate, Gd2Zr207, have been examined via high-temperature x-ray powder diffraction. Gadolinium zirconate is an ideal material for such a structure-property-processing study: it shows ordering of defects at low temperatures, taking on a pyrochlore structure, and disordering at elevated temperature, taking on a defect fluorite structure. Diffraction experiments, performed as functions of time and temperature, confirmed the transition temperature to lie between 1500 and 1550 °C. They also revealed that the transformation takes place most rapidly just below the transition temperature, indicating that the ordering process is kinetically constrained at low temperatures. Moreover, x-ray data collected at room temperature from quenched samples were found to be as useful, if not more so, than those collected in situ at high temperature. The latter are affected by thermal scattering, severely compromising data quality.

BaZn2Si2O7 and the solid solution series BaZn2−xCoxSi2O7 (0

2013 ◽  
Vol 207 ◽  
pp. 55-60 ◽  
Author(s):  
Marita Kerstan ◽  
Christian Thieme ◽  
Matthias Grosch ◽  
Matthias Müller ◽  
Christian Rüssel
Keyword(s):  
Solid Solution ◽  
Fuel Cells ◽  
High Temperature ◽  
Solid Oxide Fuel Cells ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Solid Solution Series ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solution Series

scholarly journals Influence of Isovalent ‘W’ Substitutions on the Structure and Electrical Properties of La2Mo2O9 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells

Ceramics ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 502-515
Author(s):  
Tanmoy Paul ◽  
Yoed Tsur
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Solid Oxide Fuel Cells ◽  
Solid Oxide ◽  
Cubic Phase ◽  
Oxide Fuel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Ion Conductivity ◽  
Oxide Ion

Lanthanum molybdenum oxide (La2Mo2O9, LAMOX)-based ion conductors have been used as potential electrolytes for solid oxide fuel cells. The parent compound La2Mo2O9 undergoes a structural phase transition from monoclinic (P21) to cubic (P213) at 580 °C, with an enhancement in oxide ion conductivity. The cubic phase is of interest because it is beneficial for oxide ion conduction. In search of alternative candidates with a similar structure that might have a stable cubic phase at lower temperatures, we have studied the variations of the crystal structure and ionic conductivity for 25, 50, 62.5 and 75 mol% W substitutions at the Mo site using high-temperature X-ray diffraction, dilatometry, and impedance spectroscopy. Highly dense ceramic samples have been synthesized by solid-state reaction in a two-step sintering process. Low-angle X-ray diffraction and Rietveld refinement confirm the stabilization of the cubic phase for all compounds in the entire temperature range considered. The substitutions of W at the Mo site produce a decrement in the lattice parameter. The thermal expansion coefficients in the high-temperature range of the W-substituted ceramics, as determined by dilatometry, are much higher than that of the unmodified sample. The impedance spectra have been modeled using a modified genetic algorithm within 300–600 °C. A distribution function of the relaxation times is obtained, and the contributions of ohmic drop, grains and grain boundaries to the conductivity have been identified. Overall, our investigation provides information about cationic substitution and insights into the understanding of oxide ion conductivity in LAMOX-based compounds for developing solid oxide fuel cells.

scholarly journals A Bulk-Heterostructure Nanocomposite Electrolyte of Ce0.8Sm0.2O2-δ–SrTiO3 for Low-Temperature Solid Oxide Fuel Cells

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yixiao Cai ◽  
Yang Chen ◽  
Muhammad Akbar ◽  
Bin Jin ◽  
Zhengwen Tu ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Ionic Conductivity ◽  
Low Temperature ◽  
Solid Oxide Fuel Cells ◽  
Short Circuit ◽  
Solid Oxide ◽  
Superior Performance ◽  
Electrode Polarization ◽  
Oxide Fuel ◽  
Ac Impedance Analysis

AbstractSince colossal ionic conductivity was detected in the planar heterostructures consisting of fluorite and perovskite, heterostructures have drawn great research interest as potential electrolytes for solid oxide fuel cells (SOFCs). However, so far, the practical uses of such promising material have failed to materialize in SOFCs due to the short circuit risk caused by SrTiO3. In this study, a series of fluorite/perovskite heterostructures made of Sm-doped CeO2 and SrTiO3 (SDC–STO) are developed in a new bulk-heterostructure form and evaluated as electrolytes. The prepared cells exhibit a peak power density of 892 mW cm−2 along with open circuit voltage of 1.1 V at 550 °C for the optimal composition of 4SDC–6STO. Further electrical studies reveal a high ionic conductivity of 0.05–0.14 S cm−1 at 450–550 °C, which shows remarkable enhancement compared to that of simplex SDC. Via AC impedance analysis, it has been shown that the small grain-boundary and electrode polarization resistances play the major roles in resulting in the superior performance. Furthermore, a Schottky junction effect is proposed by considering the work functions and electronic affinities to interpret the avoidance of short circuit in the SDC–STO cell. Our findings thus indicate a new insight to design electrolytes for low-temperature SOFCs.

scholarly journals Remarkable Ionic Conductivity in a LZO-SDC Composite for Low-Temperature Solid Oxide Fuel Cells

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2277
Author(s):  
Zhengwen Tu ◽  
Yuanyuan Tian ◽  
Mingyang Liu ◽  
Bin Jin ◽  
Muhammad Akbar ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Ionic Conductivity ◽  
Low Temperature ◽  
Solid Oxide Fuel Cells ◽  
Ionic Conduction ◽  
Open Circuit ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Open Circuit Voltages ◽  
Composite Samples

Recently, appreciable ionic conduction has been frequently observed in multifunctional semiconductors, pointing out an unconventional way to develop electrolytes for solid oxide fuel cells (SOFCs). Among them, ZnO and Li-doped ZnO (LZO) have shown great potential. In this study, to further improve the electrolyte capability of LZO, a typical ionic conductor Sm0.2Ce0.8O1.9 (SDC) is introduced to form semiconductor-ionic composites with LZO. The designed LZO-SDC composites with various mass ratios are successfully demonstrated in SOFCs at low operating temperatures, exhibiting a peak power density of 713 mW cm−2 and high open circuit voltages (OCVs) of 1.04 V at 550 °C by the best-performing sample 5LZO-5SDC, which is superior to that of simplex LZO electrolyte SOFC. Our electrochemical and electrical analysis reveals that the composite samples have attained enhanced ionic conduction as compared to pure LZO and SDC, reaching a remarkable ionic conductivity of 0.16 S cm−1 at 550 °C, and shows hybrid H+/O2− conducting capability with predominant H+ conduction. Further investigation in terms of interface inspection manifests that oxygen vacancies are enriched at the hetero-interface between LZO and SDC, which gives rise to the high ionic conductivity of 5LZO-5SDC. Our study thus suggests the tremendous potentials of semiconductor ionic materials and indicates an effective way to develop fast ionic transport in electrolytes for low-temperature SOFCs.

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