Precipitation of iron zirconate from Zr4+-oversaturated Fe2O3−x (I)

Wu, Mingxi; Gan, Dershin; Shen, Pouyan

doi:10.1016/s0921-5093(00)01268-5

Cited by 9 publications

(4 citation statements)

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“…GP zones have also been identified in Ti‐doped MgO and Zr‐doped Fe 2 O 3 . The co‐existence of GP zones and platelets suggested that the GP zone might be an intermediate step in the nucleation and growth of SnTiO 3 .…”

Section: Resultsmentioning

confidence: 90%

“…GP zones have also been identified in Ti-doped MgO and Zr-doped Fe 2 O 3 . 17,18 The co-existence of GP zones and platelets suggested that the GP zone might be an intermediate step in the nucleation and growth of SnTiO 3 . Further detailed work is required to understand the precipitation process in relation to doping, temperature, and composition.…”

Section: Resultsmentioning

confidence: 99%

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Thermoelectric Properties of Undoped and Doped (Ti_0.75Sn_0.25)O₂

2011

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Thermoelectric properties of undoped and doped (Ti0.75Sn0.25)O2 were investigated for high‐temperature thermoelectric conversion application. Nano‐composites were formed by annealing above 1000°C. Outside the spinodal dome, ilmenite‐type SnTiO3 precipitated from the rutile structure. Thermoelectric properties were measured in the temperature range from room temperature to 1000°C. (Ti0.75Sn0.25)O2 was doped with both acceptor and donor dopants. Both undoped and doped (Ti0.75Sn0.25)O2 exhibit n‐type electrical behavior independent of the type of the dopant. The electrical conductivity was enhanced three orders of magnitude by donor doping with Nb2O5 or Ta2O5; achieving a maximum of 546 S/m at 850°C. The increase in electrical conductivity was accompanied by reduction of the absolute Seebeck coefficient. Seebeck coefficient reduction of −600 μV/K was observed between undoped and 4% Ta2O5 doped samples. The solid solution and doping reduced the thermal conductivity to <4 W/mK, far below the parent materials TiO2 and SnO2. Lattice thermal conductivity decreased with increasing temperature, achieving 1.9 W/mK at 900°C for 4% Ta2O5 doping. No further reduction in thermal conductivity was observed in annealed samples containing nano‐sized SnTiO3 precipitates. Dimensionless figure of merit (ZT) attained was <0.1.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Thermoelectric Properties of Undoped and Doped (Ti_0.75Sn_0.25)O₂

2011

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“…The combination of characteristic morphologies and diffraction patterns indicate that this low tetragonal phase may appear to be cubic, but tetragonal prime phase. Additionally, some of faint diffraction spots (marked in green circles and yellow triangles in Figures 6B and 7E,F) are not corresponding to t′ phase, but more like diffraction resulted from precipitate clusters according to its periodicity estimation 41,42 . However, no new precipitate phase was found in XRD patterns and Raman spectra.…”

Section: Resultsmentioning

confidence: 95%

“…We deduced that the precipitates should be extremely fine‐scaled (about 3–10 nm in size) solute enriched regions of the FeY‐TZP specimens, as shown by yellow arrows of Figures 6C–E and 7E, may be the early‐stage t′ phase. The similar solute clusters, named as GP I/II zones, are commonly found in Al‐Cu‐Mg alloys 42,43 and Zr‐doped oversaturated Fe 2 O 3 solids 41 experienced an age hardening procedure, because the supersaturated solid solution undergoes a transformation with the alloying atoms diffusing through the host lattice to form solute‐rich clusters, offering physical obstructions to the motion of dislocations.…”

Section: Resultsmentioning

confidence: 99%

Effect of doping location induced anisotropy on thermophysical properties of dilute Fe₂O₃‐Y₂O₃‐ZrO₂ solid solutions

et al. 2021

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Multi‐element doped zirconia ceramics are of interest as a satisfactory balance in low thermal conductivity, phase stability, and particularly fracture resistance dominated by non‐transformable tetragonal prime phase (t′) for the next generation thermal barrier coatings and catalysis supports. Compared with mass and radius of dopants, dopant location is rarely investigated due to the high complexity. The undersized transition metal oxides (Fe, Co, and Ni) within 2.0 mol% content were selected for doping 3Y‐TZP to improve thermophysical properties by distinctive doping locations. As shown by X‐ray diffraction and Raman spectra, the Fe3+/Fe2+ ions occupied both substitution and interstitial sites simultaneously, which significantly increased tetragonality and local anisotropy of FeY‐TZP polycrystal. The t′ phase transformation mechanism of the FeY‐TZP compounds quantitatively discussed regarding the coercive strain and stress. In opposition to prediction by Kopp's law, the coefficient of thermal expansion and specific heat capacity of the FeY‐TZP compounds unusally decreased, and the maximum reduction of −83% and −22.5% occured in the 1.0 mol% Fe doping. Cp‐T dependency of the specimens above 550 K strongly related with lattice anisotropy in addition to t′ phase content. Thermomechanical properties of the multicomponent zirconia are highly tunable with dopant locations, supplying a novel landscape for designing high‐entropy ceramics.

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