Low temperature synthesis of nanocrystalline Y2Ti2O7, Y2Zr2O7, Y2Hf2O7 with exceptional hardness by reverse co-precipitation technique

Karthick, G.; Karati, Anirudha; Murty, B.S.

doi:10.1016/j.jallcom.2020.155491

Cited by 20 publications

(12 citation statements)

References 39 publications

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“…The values of R p and Rw p are 4.51% and 6.44%, respectively, indicating that the refinement result is reliable. Furthermore, the six Raman peaks of pyrochlore oxide (E g + A 1g + 4F 2g ) and three typical Raman peaks of YNbO 4 (v 1 + v 2 + v 4 ) are found in the Raman spectrum, 36,47,48 as shown in Figure S1B. The other two peaks at 133.6 and 237.7 cm −1 also belong to the monoclinic YNbO 4 due to its external vibrations 48 .…”

Section: Resultsmentioning

confidence: 89%

“…Y 2 TiO 7 has a cubic pyrochlore structure, while Y 2 Zr 2 O 7 and Y 2 Hf 2 O 7 have the cubic defect fluorite structure. 36,37 Defect fluorite structure can be regarded as the disordered pyrochlore structure, in which all the metal cations occupy A and B sites randomly, 38,39 as shown in Figure 1A,B. The crystal structure of A 2 B 2 O 7type oxide depends on the radius ratio of A-site and B-site cations (R A /R B ).…”

Section: Introductionmentioning

confidence: 99%

“…The crystal structures of these compounds are different. Y 2 TiO 7 has a cubic pyrochlore structure, while Y 2 Zr 2 O 7 and Y 2 Hf 2 O 7 have the cubic defect fluorite structure 36,37 . Defect fluorite structure can be regarded as the disordered pyrochlore structure, in which all the metal cations occupy A and B sites randomly, 38,39 as shown in Figure 1A,B.…”

Section: Introductionmentioning

confidence: 99%

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High‐entropy yttrium pyrochlore ceramics with glass‐like thermal conductivity for thermal barrier coating application

et al. 2022

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A 2 B 2 O 7 -type oxides with low thermal conductivities are potential candidates for next-generation thermal barrier coatings. The formation of high-entropy ceramics is considered as a newly effective way to further lower their thermal conductivities. High-entropy Y 2 (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 ) 2 O 7 (5HEO) and Y 2 (Ti 0.25 Zr 0.25 Hf 0.25 Ta 0.25 ) 2 O 7 (4HEO) ceramics were prepared by in situ solid reaction sintering, considering the important roles of B-site cations on thermal conductivities of the A 2 B 2 O 7 -type oxides. Reaction process, phase structures, microstructures, and thermal conductivities of the as-sintered ceramics were investigated. Lattice distortion effects on their thermal conductivities were also discussed by using the proposed criterion based on the supercell volume difference of the individual compounds. Near fully-dense 5HEO and 4HEO ceramics were obtained after being sintered at 1600 • C. The former one had a dual-phase structure containing high-entropy Y 2 (Ti 0.227 Zr 0.227 Hf 0.227 Nb 0.136 Ta 0.182 ) 2 O 7.318 pyrochlore oxide (5HEO-P) and Y(Nb, Ta)O 4 solid solution, while the latter one was a single-phase pyrochlore oxide (4HEO-P) with homogeneous element distribution. The formed 5HEO-P oxide has larger lattice distortion than 4HEO-P oxide due to the larger total amounts of Nb and Ta cations at B sites in the 5HEO-P oxide. It results in lower thermal conductivity of 5HEO ceramics (keeping at 1.8 W⋅m -1 ⋅K -1 ) than those of 4HEO ceramics (ranging from 1.8 to 2.5 W⋅m -1 ⋅K -1 ) at temperatures from 25 • C to 1400 • C. Their glass-like thermal conductivities were determined by the selection of B site cations and high-entropy effects. These results provide some useful information for the material design of novel thermal barrier coating materials.

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Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High‐entropy yttrium pyrochlore ceramics with glass‐like thermal conductivity for thermal barrier coating application

et al. 2022

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“…where β = 10 7 s -1 and α0 = 4.5 (± 1) × 10 -3 cm -1 [46,47], ∆E1 is energy gap between 3 P0 and 1 D2 of about 3500 cm -1 [48], and �υmax is the maximum phonon energy of YZO lattice (~ 660 cm -1 ) [35,49,50].…”

Section: Temperature-dependent Photoluminescence Behaviormentioning

confidence: 99%

Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows

Lu¹,

Ye²,

Han³

et al. 2023

Journal of Advanced Ceramics

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Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments, however, obtaining efficient photoluminescence together with high transparency in these ceramics is still posing serious challenges, which undoubtedly limits their applications. Here, Pr-doped Y2Zr2O7 (YZO) transparent ceramics, as an illustrative example, are prepared by a solid-state reaction and vacuum sintering method. Owing to the elimination of defect clusters [𝑃𝑃𝑃𝑃 𝑌𝑌 4 + -𝑂𝑂 2− -𝑃𝑃𝑃𝑃 𝑌𝑌 4 + ] and [𝑃𝑃𝑃𝑃 𝑌𝑌 4 + -𝑒𝑒 ′ ] without introduction of impurities and additional defects, the fabricated YZO:Pr ceramics exhibit high transparency (74 %) and efficient photoluminescence (39-fold enhanced) after air annealing plus vacuum re-annealing treatment. Moreover, upon 295/450 nm excitation, the emission bands (blue, green, red, and dark red) from YZO:Pr ceramic present different temperature-dependent properties due to the thermal quenching channel generated by the intervalence charge transfer state (IVCT) between Pr 3+ and Zr 4+ ions. Furthermore, a self-calibrated temperature feedback window with same FIR model (I613/I503) under different excitation light sources (295 nm and 450 nm) is designed. The developed photothermal window operated in a wide temperature range (303 -663 K) shows relatively high sensitivities (Sa andSr reach 0.008 K -1 at 663 K and 0.47 % K -1 at 363 K, respectively), high repeatability (> 98 %), and low temperature uncertainty (< 3 K). This work presents a paradigm for achieving enhanced photoluminescence along with elevated transparency of lanthanides doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.

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“…A microwave hydrothermal route [ 59 ] provided pyrochlore-structured Y 2 Ti 2 O 7 on calcination at temperatures 950 and 1050 °C. Reduction of the temperature during the Y 2 Ti 2 O 7 synthesis was achieved through the Reverse Co-precipitation (RCP) technique [ 60 ].…”

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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Low temperature synthesis of nanocrystalline Y2Ti2O7, Y2Zr2O7, Y2Hf2O7 with exceptional hardness by reverse co-precipitation technique

Cited by 20 publications

References 39 publications

High‐entropy yttrium pyrochlore ceramics with glass‐like thermal conductivity for thermal barrier coating application

High‐entropy yttrium pyrochlore ceramics with glass‐like thermal conductivity for thermal barrier coating application

Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows

Novel Microwave-Assisted Method of Y2Ti2O7 Powder Synthesis

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