Preparation and high temperature-XRD studies on a pyrochlore series with the general composition Gd2−xNdxZr2O7

Mandal, Balaji P.; Tyagi, A. K.

doi:10.1016/j.jallcom.2006.07.093

Cited by 91 publications

(35 citation statements)

References 19 publications

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“…It can be seen that (Ln 0.9 Gd 0.05 Yb 0.05 ) 2 Zr 2 O 7 (Ln = Sm, Nd) ceramics are with a single phase structure, pyrochlore-type lattice, which is characterized by the presence of typical super-lattice peaks at 2 h values of about 14°(111), 28°(311), 37°(331) and 45°(511) using Cu Ka radiation. [17,18] In the Ln 2 Zr 2 O 7 system, the phase structure is mostly determined by the ionic radius ratio of r(Ln 3+ )/r(Zr 4+ ). The pyrochlore structure stability field at an atmospheric pressure in zirconates is limited to the range of 1.46 ≤ r(Ln 3+ )/r(Zr 4+ ) ≤ 1.78.…”

Section: Resultsmentioning

confidence: 99%

(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

et al. 2008

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Ceramic thermal barrier coatings (TBCs) used for thermal insulation against hot combustion gases greatly enhance operating temperatures and thermal efficiency of hot-section components in gas-turbine engines, and reduce fuel consumption and gas emissions at elevated temperatures. [1][2][3] Up to now, the most successful TBC materials in use are 7 ± 1 wt.%Y 2 O 3 stabilized ZrO 2 (7YSZ). However, 7YSZ is limited to operate below 1200°C. Above 1200°C, the t'-phase zirconia transforms into tetragonal and cubic phases. During cooling the tetragonal phase will further transform into monoclinic phase, which is accompanied with a volume change of 3-5 % and invariably causes cracking and failure. The relatively porous 7YSZ plasma-sprayed coatings are prone to sintering above 1200°C, which increases thermal conductivity and makes them less effective. To further improve the thermal insulation properties, it is urgently needed to develop new thermal barrier oxide materials with a lower thermal conductivity than 7YSZ. Some important requirements for excellent TBC materials are high melting point, high phase stability, low thermal conductivity, chemical inertness, high thermal expansion coefficient, high strain tolerance and low sintering rate at elevated temperatures. [4] Among high-melting temperature ceramic materials, rareearth zirconates, with the general formula Ln 2 Zr 2 O 7 (Ln = La, Nd, Sm, Eu, Gd, etc), have a distinctly lower thermal conductivity than 7YSZ. [5,6] Pyrochlore-structured La 2 Zr 2 O 7 -based TBCs were successfully prepared with electron beam physical vapor deposition (EB-PVD) method by Saruhan et al. [7] The hot corrosion resistance of La 2 Zr 2 O 7 coatings was better than that of 8 wt.% yttria-stabilized zirconia coatings produced by thermal spraying, and La 2 Zr 2 O 7 coatings remained well bonded to the substrate following exposure to vanadium compound at 1000°C. [8] La 2 Zr 2 O 7 TBCs exhibited a better thermal cycling performance of 1865 cycles at 1050°C than EB-PVD 7YSZ (1380 cycles) TBCs. [9] The rare-earth zirconate pyrochlore/YSZ double-layer material systems produced by atmospheric plasma spraying had a longer thermal cycling life than the single layer YSZ coatings. This indicates that the double-layer structure was an efficient way to use the advantages and overcome the disadvantages of different coating materials, giving promise to the application of the TBCs at temperatures higher than 1250°C. [10,11] It was reported that the substitution of some Ln sites in Ln 2 Zr 2 O 7 by other rareearth cations led to a low thermal conductivity as contrasted with pure rare-earth zirconates. [12][13][14] In the present study, Ln 2 Zr 2 O 7 (Ln = Sm, Nd) ceramics codoped with both 5 mol.%Gd and 5 mol.%Yb were prepared in order to further reduce thermal conductivity, and microstructure and thermophysical properties of (Ln 0.9 Gd 0.05 Yb 0.05 ) 2 Zr 2 O 7 (Ln = Sm, Nd) ceramics were examined. Experimental ProcedureIn the present study, rare earth oxide powders (Nd ; purity ≥ 99.99 %) and zirconium oxychl...

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Section: Resultsmentioning

confidence: 99%

(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

et al. 2008

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“…Gd 2 Zr 2 O 7 exhibits a defect fluorite-type structure. However, structures of (Sm x Gd 1−x ) 2 Zr 2 O 7 (0.1 ≤ x ≤ 1.0) ceramics doped with different contents of Sm 3+ ions transform into an ordered pyrochlore-type structure, which is characterized by the presence of typical super-lattice peaks at 2Â values of about 14 • (1 1 1), 28 • (3 1 1), 37 • (3 3 1) and 45 • (5 1 1) using Cu K␣ radiation [15][16][17][18], as shown in Fig. 4.…”

Section: Characterization Of (Sm X Gd 1−x ) 2 Zr 2 O 7 Bulk Ceramicsmentioning

confidence: 99%

Structural evolution and thermophysical properties of (SmxGd1−x)2Zr2O7 (0≤x≤1.0) ceramics

Liu

Ouyang

Zhou

2009

Journal of Alloys and Compounds

103

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“…Pyrochlore type of rare earth zirconium oxides (Re 2 Zr 2 O 7 , Re = rare earth) has received considerable attention in recent years [3,4]. Great interests have been focused on the synthesis and investigation of the properties of Re 2 Zr 2 O 7 , due to their excellent properties, such as low thermal conductivity, high thermal expansion coefficient, metal-insulator transitions, geometrically frustrated Kagome-type spin lattices, dielectric properties [5,6].…”

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of Ln2Zr2O7 (Ln=La and Nd) nanocrystals and their photocatalytic properties

Tong

Zhu

et al. 2008

Journal of Alloys and Compounds

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Preparation and high temperature-XRD studies on a pyrochlore series with the general composition Gd2−xNdxZr2O7

Cited by 91 publications

References 19 publications

(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

Structural evolution and thermophysical properties of (SmxGd1−x)2Zr2O7 (0≤x≤1.0) ceramics

Preparation and characterization of Ln2Zr2O7 (Ln=La and Nd) nanocrystals and their photocatalytic properties

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Preparation and high temperature-XRD studies on a pyrochlore series with the general composition Gd2−xNdxZr2O7

Cited by 91 publications

References 19 publications

(Ln0.9Gd0.05Yb0.05)2Zr2O7 Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

(Ln0.9Gd0.05Yb0.05)2Zr2O7 Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

Structural evolution and thermophysical properties of (SmxGd1−x)2Zr2O7 (0≤x≤1.0) ceramics

Preparation and characterization of Ln2Zr2O7 (Ln=La and Nd) nanocrystals and their photocatalytic properties

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(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides

(Ln_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ Ceramics with Pyrochlore Structure as Thermal Barrier Oxides