Investigation on microstructures and thermo-physical properties of ferroelastic (Y1-xDyx)TaO4 ceramics

Gan

et al. 2020

Mater. Res. Express

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SmTaO 4 , Sm 3 TaO 7 and SmTa 3 O 9 ceramics were prepared via a high temperature solid-state reaction. The results show that the phase structures of the SmTaO 4 ceramics are a monoclinic phase (space group: I2 (5)), the Sm 3 TaO 7 ceramics are an ordered orthorhombic phase (space group: Ccmm), and the SmTa 3 O 9 ceramics are an orthorhombic phase (space group: Cmmm). Macromolecular and crystal structures of Sm 3 TaO 7 and SmTa 3 O 9 are more complex than those of SmTaO 4 , which can enhance phonon scattering and reduce thermal conductivity. Compared with those of SmTaO 4 and SmTa 3 O 9 , Sm 3 TaO 7 has the smallest grain size, indicating that a small grain size has an effect on strength and ensures material stability. Because of a distorted TaO 6 octahedron and a high concentration of cation vacancy in the lattice of SmTa 3 O 9 , its thermal conductivity increases with increasing temperature. Compared with that of 7-8 YSZ, Sm 3 TaO 7 has a low thermal conductivity (1.3-1.7 W·m −1 ·K −1 at 100°C-900°C), and its minimum thermal conductivity is nearly 30% lower than that of YSZ. The Sm 3 TaO 7 ceramics have the highest TECs at approximately 9.82×10 −6 K −1 at 1200°C, which is close to that of 7-8 YSZ (approximately 10×10 −6 ). This indicates that Sm 3 TaO 7 has the potential to be employed as a thermal barrier coating.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermophysical properties of SmTaO₄, Sm₃TaO₇ and SmTa₃O₉ ceramics

Gan

et al. 2020

Mater. Res. Express

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“…The ferroelastic domains also appears in RETaO 4 ceramics and has been systematically investigated . According to related literature, the ferroelastic domain of RETaO 4 ceramics is originated from the phase transition between high‐temperature t phase and low‐temperature m phase, so it can be regarded as the sign of ferroelastic transformation. The appearance of ferroelastic domain in the morphologies of RENbO 4 ceramics also suggests that the t‐m phase transformation of RENbO 4 ceramics is also ferroelastic transformation.…”

Section: Resultsmentioning

confidence: 99%

The thermo‐mechanical properties and ferroelastic phase transition of RENbO₄ (RE = Y, La, Nd, Sm, Gd, Dy, Yb) ceramics

et al. 2019

J Am Ceram Soc

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In this work, RENbO4 (RE = Y, La, Nd, Sm, Gd, Dy, Yb) ceramics with low density, low Young's modulus, low thermal conductivity, and high thermal expansion have been systematically investigated, the excellent thermo‐mechanical properties indicate that RENbO4 ceramics possess the potential as the new generation of thermal barrier coatings (TBCs) materials. X‐ray diffraction and Raman spectroscopy phase structure identification reveal that all dense bulk specimens obtained by high‐temperature solid‐state reaction belonged to the monoclinic (m) phase with C12/c1 space group. The ferroelastic domains are detected in the specimens, revealing the ferroelastic transformation between tetragonal (t) and monoclinic (m) phases of RENbO4 ceramics. The Young's modulus and hardness of the RENbO4 ceramics measured by the NanoBlitz 3D nanoindentation method are discussed in details, and the lower Young's modulus (60‐170 GPa) and higher hardness (the maximum value reaches 11.48 GPa) indicating that higher resistance of RENbO4 ceramics to failure and damage. Lower thermal conductivity (1.42‐2.21 W [m k]−1 at 500°C‐900°C) and lower density (5.330‐7.400 g/cm3) than other typical TBCs materials give RENbO4 ceramics the unique advantage of being new TBCs materials. Meanwhile, the thermal expansion coefficients of RENbO4 ceramics reach 9.8‐11.6 × 10−6 k−1 and are comparable or higher than other typical TBCs materials. According to the first‐order derivative of the thermal expansion rate, the temperature of the ferroelastic transformation of RENbO4 ceramics can be observed.

“…23 Impregnation of alumina matrix in eight-harness satin Nextel 610 fabric has been studied numerically in Ref. [ 24 ]. Modeling approaches used in the above work generally involved modeling the flow of a high viscosity resin through porous media and modeling the chemical reactions and volumetric changes during processing.…”

Section: Introductionmentioning

confidence: 99%

First‐principles study of thermophysical properties of polymorphous YTaO₄ ceramics

Gan

et al. 2021

J Am Ceram Soc.

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Yttrium tantalate ceramics with ferroelasticity are potential candidates for thermal barrier coating (TBC) ceramics. During the phase transition process, there are three main phases with monoclinic (I2/a), monoclinic-prime (P2/a), and tetragonal structures (I 41 /a), and a comprehensive understanding of their thermophysical properties is required. In this study, the thermal and mechanical properties of polymorphous yttrium tantalate (YTaO 4 ) ceramics are systematically investigated under finite temperature by performing first-principles calculations combined with quasi-harmonic approximation. The first-principle study results show that the volume change from M' to T phase is 12.85 Å 3 to 12.95 Å 3 per atom, whereas the T to M is 12.95 Å 3 to 12.84 Å 3 per atom, and the change is less than 1%, showing that this process produces almost no volume change.However, the thermal expansion coefficients (TECs) and Young's modulus vary greatly, the TECs value of M YTaO 4 is about 11.13 × 10 −6 K −1 , which is smaller than T YTaO 4 as the value 12.01 × 10 −6 K −1 , and the Young's modulus values of M, M', and T phases are 140. 34, 156.68, and 123.29 GPa, respectively. Lastly, the calculated O-Ta bond is stronger than the O-O and O-Y bonds according to the mean bond population and average bond length, resulting in a higher modulus. This work will not only expand the internal mechanism of the thermophysical properties of YTaO 4 , but also provides support for the design and application of TBC systems.