Microstructure and crystallography of Al2O3–Y3Al5O12–ZrO2 ternary eutectic oxide grown by the micropulling down technique

Benamara, O.; Cherif, Maya; Duffar, T.; Lebbou, Kheirréddine

doi:10.1016/j.jcrysgro.2015.07.020

Cited by 44 publications

(21 citation statements)

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“…At least part of the motivation for the polycrystalline research was to investigate the stress fields arising in polycrystalline alumina responsible for microcracking-the spontaneous localized cracking that occurs in polycrystalline alumina on cooling as a consequence of the anisotropic structure and thermal expansion of corundum [39][40][41]. From the 1990s onward, although there were many notable fundamental studies of the phenomenon [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], the shift in energy of R lines with stress was largely confined to the applied domain, detailed in numerous works, such as: measurement of stress in bulk Al2O3 polycrystals [42,[58][59][60][61][62][63][64][65][66][67]; in bulk Al2O3-ZrO2 composites [68][69][70][71][72][73][74][75][76][77][78]; in sapphire or composite fibers, free or in matrices [79][80]…”

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confidence: 99%

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Cook

Michaels

2017

J. RES. NATL. INST. STAN.

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The numerical coefficients linearly relating the effects of stress (including pressure), temperature, and composition to shifts in the energies of the Cr-related fluorescence in alumina (Al2O3) are reviewed. The primary focus is the shift of the R1 and R2 “ruby” fluorescence lines under conditions typical for stress determination in polycrystalline Al2O3. No significant experimental difference in the R1 and R2 responses is observed for hydrostatic stress (or pressure) conditions (average shift coefficient of about 7.6 cm−1/GPa), changes in temperature (about 0.140 cm−1/K), or variations in composition (about 120 cm−1/mass fraction of Cr). There are significant differences in the R1 and R2 responses for nonhydrostatic stress conditions. In particular, for uniaxial stress along the a and c directions in the Al2O3 crystal, the R1 piezospectroscopic tensor coefficients (about 3.0 cm−1/GPa and 1.6 GPa cm−1/GPa, respectively) differ considerably, whereas the R2 coefficients (about 2.6 cm−1/GPa and 2.3 GPa cm−1/GPa, respectively) do not. Measurements of the piezospectroscopic tensor coefficients are shown to have interlaboratory relative consistency of about 4 % extending over 30 years, and are consistent with the scalar high-pressure measurements. Measurements of the temperature coefficients are shown to have interlaboratory relative consistency less than 1 % extending over 60 years. Fluorescence-based measurements of stress in polycrystalline Al2O3, although requiring temperature adjustment, are shown to have a relative uncertainty of about 2.5 %.

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confidence: 99%

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Cook

Michaels

2017

J. RES. NATL. INST. STAN.

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“…2,3 These excellent high-temperature performances make it promising for extreme working conditions such as hot-end components in advanced aero engines and heavy gas turbines. 4 At present, the preparation methods of melt-grown ceramics mainly include directional solidification methods such as the Bridgman, the micro-pulling down, laser floating zone melting, [5][6][7] and nondirectional solidification methods such as combustion synthesis and explosion synthesis. 8,9 Among these methods, the micropulling down and laser floating zone melting are difficult to prepare large cross-sectional (above centimeters or more) structures.…”

Section: Introductionmentioning

confidence: 99%

Effect and mechanism of ZrO₂ doping on the cracking behavior of melt‐grown Al₂O₃ ceramics prepared by directed laser deposition

San

Niu

et al. 2019

Int J Applied Ceramic Tech

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Directed laser deposition (DLD) is a new method for rapidly preparing melt-grown ceramics, but cracking problem greatly limited its application. In this study, cracking behavior of Al 2 O 3 ceramics was suppressed by doping ZrO 2. Crack suppression mechanism of ZrO 2 doping in melt-grown ceramics was also analyzed. Process parameters which are prone to generating cracks were adopted in the experiments, and they contribute to showing the crack clearly. Results show that ZrO 2 doping has remarkable crack suppression effects. It is most obvious when ZrO 2 content is 37 mol%. Compared with those of pure Al 2 O 3 ceramics, crack density reduces by 43.2%, and the number of longitudinal main cracks reduces by 63.2%. Doping of ZrO 2 forms dense composite microstructure with primary α-Al 2 O 3 grains discretely distributing in eutectic continuous matrix. Therefore, initial crack sources are effectively reduced. Morphology of primary Al 2 O 3 grains transforms from cellular to dendritic, which changes crack propagation mode from inter-granular to trans-granular. Mismatch of thermo-physical properties of different phase promotes the arrest, deflection, and bridging phenomena in crack propagation, contributing to crack suppression. On the basis of ZrO 2 doping, we have realized the preparation of crack-free eutectic ceramic (37 mol%ZrO 2) samples through further process optimization. The maximum size of the sample reaches 230 mm.

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“…Eutectic ceramic oxides grown by directional solidification are of interest for structural applications at high temperatures. Promising materials in this respect are Al 2 O 3 /Y 3 Al 5 O 12 (Al 2 O 3 /YAG), Al 2 O 3 /Er 3 Al 5 O 12 , Al 2 O 3 /GdAlO 3 and Al 2 O 3 /YAG/ZrO 2 . For example, the ternary eutectic composite Al 2 O 3 /YAG/ZrO 2 displays excellent mechanical properties at high temperatures .…”

Section: Introductionmentioning

confidence: 99%

“…According to Lakiza, two parameters show a significant impact on defect formation in directionally solidified eutectic ceramics: the growth rate and the temperature gradient at the solidification front. Various crystallization methods are used to investigate these composites: Bridgman, laser‐heated floating zone, micro‐pulling down, Edge‐defined Film‐fed Growth (EFG), and Czochralski method (Cz) …”

Section: Introductionmentioning

confidence: 99%

“…Micro‐pulling down method was used to grow Al 2 O 3 /YAG/ZrO 2 rods of 5 mm in diameter and ribbons of 10 mm in width and 2.4 mm in thickness . Ceramic rods solidified at low rates (<6 mm/h) presented a fine and uniform structure, while a colony type microstructure appeared in the ingots grown at higher pulling rates . X‐ray diffraction patterns of the samples have shown that the crystallographic orientation of the phases changes at high growth rates (60 mm/h).…”

Section: Introductionmentioning

confidence: 99%

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Growth rate effect on colony formation in directional solidification of Al₂O₃/YAG/ZrO₂

et al. 2018

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Mechanical properties of Al 2 O 3 /Y 3 Al 5 O 12 /ZrO 2 ternary eutectic ceramics are strongly affected by structural defects as pores or colonies. Experimental investigation of the microstructure of this ternary composite indicates that the colonies are generally observed when the solidification occurs at high rates. In this work, the influence of the growth rate on the solid-liquid interface shape and formation of colonies in directional solidification of Al 2 O 3 /Y 3 Al 5 O 12 /ZrO 2 by Bridgman, Edge-defined Film-fed Growth (EFG), and Czochralski (Cz) methods is numerically and experimentally investigated. Numerical modeling of the Bridgman growth process shows large curvatures of the solid-liquid interface when the pulling rate is increased up to 80 mm/h. The ingots solidified at rates between 5 and 80 mm/h exhibit colony type microstructure. The analysis of EFG growth of ceramic ribbons reveals less curved solid-liquid interfaces in this system. Numerical modeling shows significant increase in the interface curvature with increasing pulling rate. The microstructure of ribbons grown at pulling rates between 6 and 12 mm/h exhibits colonies only for the ingots solidified at higher rate. Simula-

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Microstructure and crystallography of Al2O3–Y3Al5O12–ZrO2 ternary eutectic oxide grown by the micropulling down technique

Cited by 44 publications

References 25 publications

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Effect and mechanism of ZrO₂ doping on the cracking behavior of melt‐grown Al₂O₃ ceramics prepared by directed laser deposition

Growth rate effect on colony formation in directional solidification of Al₂O₃/YAG/ZrO₂

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Microstructure and crystallography of Al2O3–Y3Al5O12–ZrO2 ternary eutectic oxide grown by the micropulling down technique

Cited by 44 publications

References 25 publications

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

Effect and mechanism of ZrO2 doping on the cracking behavior of melt‐grown Al2O3 ceramics prepared by directed laser deposition

Growth rate effect on colony formation in directional solidification of Al2O3/YAG/ZrO2

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Effect and mechanism of ZrO₂ doping on the cracking behavior of melt‐grown Al₂O₃ ceramics prepared by directed laser deposition

Growth rate effect on colony formation in directional solidification of Al₂O₃/YAG/ZrO₂