Role of sintering temperature on thermal, electrical and structural properties of Y2Ti2O7 pyrochlores

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

doi:10.1016/j.ijhydene.2011.02.138

Cited by 22 publications

(17 citation statements)

References 24 publications

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“…Therefore, an important task is to find alternative materials, which have higher or similar proton conductivity compared with well-known BaZr 0.8 Y 0.2 O 3−δ perovskite proton conductor, but the problem of low grain-boundary conductivity, which limits the total conductivity of BaZr 0.8 Y 0.2 O 3−δ , should disappear in these new materials. Although there are numerous experimental studies discussing the effect of chemistry and/or disorder on ionic conductivity of pyrochlores [2,3,4,5,6,7,8,9,10,11,12,13,14], there are only a few that examine the impact of GBs (grain boundaries) on oxygen and proton diffusion in pyrochlores [15,16,17,18].…”

Section: Introductionmentioning

confidence: 99%

“…Ln 2 Zr 2 O 7 zirconates have long been studied as potential solid electrolytes for SOFCs [2,6,8,9,11,12,13]. Among undoped Ln 2 Zr 2 O 7 zirconates, the highest oxygen-ion conductivity is offered by Gd 2 Zr 2 O 7 , the most disordered pyrochlore oxide and an intrinsic oxygen-ion conductor (cation anti-site and related oxygen vacancies formation in the pyrochlore structure) [9].…”

Section: Introductionmentioning

confidence: 99%

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Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

et al. 2019

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Sm2−xCaxZr2O7−x/2 (x = 0, 0.05, 0.1) and Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1) mixed oxides in a pyrochlore–fluorite morphotropic phase region were prepared via the mechanical activation of oxide mixtures, followed by annealing at 1600 °C. The structure of the solid solutions was studied by X-ray diffraction and refined by the Rietveld method, water content was determined by thermogravimetry (TG), their bulk and grain-boundary conductivity was determined by impedance spectroscopy in dry and wet air (100–900 °C), and their total conductivity was measured as a function of oxygen partial pressure in the temperature range: 700–950 °C. The Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) pyrochlore solid solutions, lying near the morphotropic phase boundary, have proton conductivity contribution both in the grain bulk and on grain boundaries below 600 °C, and pure oxygen–ion conductivity above 700 °C. The 500 °C proton conductivity contribution of Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) is ~ 1 × 10−4 S/cm. The fluorite-like Gd2−xCaxZr2O7−x/2 (x = 0.1) solid solution has oxygen-ion bulk conductivity in entire temperature range studied, whereas proton transport contributes to its grain-boundary conductivity below 700 °C. As a result, of the morphotropic phase transition from pyrochlore Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) to fluorite-like Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1), the bulk proton conductivity disappears and oxygen-ion conductivity decreases. The loss of bulk proton conductivity of Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1) can be associated with the fluorite structure formation. It is important to note that the degree of Ca substitution in such solid solutions (Ln2−xCax)Zr2O7−δ (Ln = Sm, Gd) is low, x < 0.1. In both series, grain-boundary conductivity usually exceeds bulk conductivity. The high grain-boundary proton conductivity of Ln2−xCaxZr2O7−x/2 (Ln = Sm, Gd; x = 0.1) is attributable to the formation of an intergranular CaZrO3-based cubic perovskite phase doped with Sm or Gd in Zr sublattice.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

et al. 2019

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“…In particular, the synthesis may be performed during the formation stage of the final products. In many works, high temperatures of 1400–1500 °C and long exposure times from 12 up to 100 h or more were used to obtain powders of the synthesized pyrochlore Y 2 Ti 2 O 7 [ 52 ]. Good results were reported after high-energy ball milling with heat treatment at 1450 °C for 12 h [ 53 ].…”

Section: Introductionmentioning

confidence: 99%

Novel Microwave-Assisted Method of Y2Ti2O7 Powder Synthesis

et al. 2020

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In the paper, a novel technique for highly dispersed pyrochlore Y2Ti2O7 is proposed. The experimental results proved that the application of microwave irradiation at a certain stage of calcination allowed synthesizing of Y2Ti2O7 in much shorter time, which ensured substantial energy savings. An increase up to 98 wt.% in the content of the preferred phase with a pyrochlore-type structure Y2Ti2O7 was obtained after 25 h of yttrium and titanium oxides calcination at a relatively low temperature of 1150 °C, while the microwave-supported process took only 9 h and provided 99 wt.% of pyrochlore. The proposed technology is suitable for industrial applications, enabling the fabrication of large industrial amounts of pyrochlore without solvent chemistry and high-energy mills. It reduced the cost of both equipment and energy and made the process more environmentally friendly. The particle size and morphology did not change significantly; therefore, the microwave-assisted method can fully replace the traditional one.

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“…Fundamentally, pyrochlore compounds are characteristic ionic conductors and their functional properties can be changed by varying the processing conditions as well as with the doping of different elements on cation sublattice. Altered materials can also be used in SOFCs as solid electrolytes [5] . An ideal oxide pyrochlore having the formula as A2B2O7 can be more accurately written as A2B2O(1)6O (2), where O(1) and O(2) correspond to crystallographically distinct sites of oxygen atoms.…”

Section: Introductionmentioning

confidence: 99%

Structural study of holmium zirconate nanoparticles obtained through carbon neutral sol-gel process

et al. 2019

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The pyrochlore oxides are of potential interest as ion conducting electrolyte for intermediate temperature solid oxide fuel cell (SOFC). Nanopowders of holmium zirconate have been synthesised through ion-exchange between sodium alginate gel and metal complex solution followed by its thermal decomposition. Nanoparticles of Ho2Zr2O7 were obtained by calcining the dried gel beads at 700˚C for 2h and 6h duration respectively. An insight into calcination has been obtained employing simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). Thermal decomposition was also followed using High Temperature X-ray Diffraction (HTXRD) in static ambient atmosphere. Results from TGA/DSC and HTXRD corroborate each other. Fine crystalline nanopowders of single phase Ho2Zr2O7 could be obtained after thermal decomposition at relatively low temperature (600-700˚C). Powder X-ray diffraction (XRD) revealed that the material has crystallized as single phase cubic Ho2Zr2O7 with defect fluorite structure. XRD and Raman spectroscopy were used to analyse the local structure of holmium zirconate. XRD scans of holmium zirconate and holmium hafnate prepared through identical method have been compared and effect of cationic radius of Zr 4+ and Hf 4+ on B-site was studied. The crystallographic data obtained from XRD and transmission electron microscopy (TEM) are in good agreement with each other. This sol gel method referred also as Leeds Alginate Process (LAP) is simple, cost effective, energy efficient and carbon neutral for the preparation of pyrochlore oxides (A2B2O7) solid electrolyte material for SOFC.

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Role of sintering temperature on thermal, electrical and structural properties of Y2Ti2O7 pyrochlores

Cited by 22 publications

References 24 publications

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Novel Microwave-Assisted Method of Y2Ti2O7 Powder Synthesis

Structural study of holmium zirconate nanoparticles obtained through carbon neutral sol-gel process

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