Achieved limit thermal conductivity and enhancements of mechanical properties in fluorite RE3NbO7 via entropy engineering

Abstract

Effective governance of thermal conductivity and other properties is of significant interest for science, including the fields of thermal barrier coatings, thermoelectric materials, and limit alloys. In this study, we investigated the impact of entropy engineering on properties of fluorite RE3NbO7, and limit thermal conductivity and strengthened mechanical properties are achieved. The solution strengthening mechanism leads to an 80% increase in toughness when the intrinsic stiffness and Young's modulus of the fabricated samples are identified via nanoindentation. Thermal conductivity is as low as 1.03–1.17 W m−1 K−1 at 25–900 °C, drastically reducing the gap between experimental results and theoretical limit values of fluorite RE3NbO7. The limit thermal conductivity as well as enhanced thermal expansion coefficients (11.2 × 10−6 K−1) and mechanical properties imply that the working performance of RE3NbO7 is evidently promoted by entropy engineering.

Interaction of multicomponent disilicate (Yb0.2Y0.2Lu0.2Sc0.2Gd0.2)2Si2O7 with molten calcia-magnesia-aluminosilicate

“…The high-entropy concept originated from highentropy alloys, wherein five or more elements with an equiatomic or near-equiatomic ratio form a single phase [17]. In the high-entropy system, the multiple principal elements with equiatomic or near-equatomic ratio would increase the configuration entropy of mixing, thereby stabilizing the solid solution [18][19][20]. The concept was extended to ceramics, including oxides [21][22][23], borides [24][25][26][27], carbides [28][29][30], and silicide [31,32].…”

Structures, and Thermophysical Properties Characterizations of (La1-xHox)3NbO7 Solid Solutions as Thermal Barrier Coatings

“…The TECs and thermal conductivity of (La 1-x Ho x ) 3 NbO 7 are shown in Figure 6D to compare with other TBC oxides. The prepared (La 1-x Ho x ) 3 NbO 7 samples have lower thermal conductivity and higher TECs than current YSZ, RE 2 Zr 2 O 7 , RETaO 4 , and distinct high-entropy ceramics (HECs) (Vassen et al, 2000;Schlichting et al, 2001;Zhao et al, 2016;Chen et al, 2018b;Ren et al, 2019;Liu et al, 2020a;Liu et al, 2020b;Chen et al, 2020;Ren et al, 2020;Chen et al, 2021a;Chen et al, 2021b). It is believed that good thermal insulation performances and low thermal stress can be provided, when (La 1-x Ho x ) 3 NbO 7 ceramics are applied as TBCs.…”

“…, and other candidate oxides (Vassen et al, 2000;Feng et al, 2013;Zhao et al, 2016;Chen et al, 2018b;Li et al, 2018;Liu et al, 2019;Ren et al, 2019;Liu et al, 2020a;Liu et al, 2020b;Chen et al, 2020;Ren et al, 2020;Wu et al, 2020;Chen et al, 2021a;Chen et al, 2021b).…”

“…To study the variations of properties of RE 3 NbO 7 along with the changes of lattice structures and to provide good understanding on these series niobates, the relevant study should be performed. The lowest thermal conductivity of weberite niobates is detected in La 3 NbO 7 , and the minimum thermal conductivity of fluorite niobates is found in Ho 3 NbO 7 oxides (Chen et al, 2018b;Chen et al, 2019b;Yang et al, 2019;Chen et al, 2021a;Chen et al, 2021b). Dense (La 1-x Ho x ) 3 NbO 7 solid solutions are fabricated in this work, and their lattices, thermal conductivity, hardness, and other properties are characterized.…”

“…A 3 BO 7 -type rare earth niobates (RE 3 NbO 7 ) have been studied in the past several years, and they have orthorhombic weberite and cubic fluorite lattices, which rely on RE 3+ ionic size (Ma et al, 2008;Zhang et al, 2017;Yang et al, 2019;Chen et al, 2021a;Chen et al, 2021b;Xiang et al, 2021). The crystal structures of RE 3 NbO 7 derive from fluorite A 4 O 8 , when the four A 4+ ions are substituted by three RE 3+ and one Nb 5+ cation, and one oxygen vacancy is produced in the lattice to maintain charge balance (Wang et al, 2012;Chen et al, 2018a;Chen et al, 2021a;Chen et al, 2021b Different structural and thermophysical property features are documented in weberite and fluorite RE 3 NbO 7 oxides, and they display good thermal insulation performance (Chen et al, 2018b;Yang et al, 2019;Chen et al, 2021a;Chen et al, 2021b). The advantages of RE 3 NbO 7 as TBCs include ultralow thermal conductivity, high TECs, and competitive modulus.…”