High‐entropy ferroelastic rare‐earth tantalite ceramic: (Y_0.2Ce_0.2Sm_0.2Gd_0.2Dy_0.2)TaO₄

Abstract

Recently, in order to develop novel materials with optimized properties, "high entropy" has attracted significant attention in the field of materials research relate to structural entropy within a material. [1][2] Multi-principal high-entropy alloys and ceramics can be synthesized, which exhibit several excellent properties, such as high strength and toughness, corrosion resistance, wear resistance, thermal performance, and electrical performance, on the basis of four high-entropy effects [3][4][5][6] : (1) high-entropy effect of thermodynamics; (2) lattice distortion effect of structure; (3) hysteretic diffusion effect; and (4) cocktail effect on performance.The high-entropy can significantly improve the comprehensive performance of the materials. For example, Gild et al. 7 reported high-entropy fluorite rare-earth oxides, that is, REO 2-δ , with thermal conductivities of 1.1-2.02 W•m -1 •K -1 , therefore, REO 2-δ has shown potential as low-thermal-conductivity materials. Ren et al. 8 synthesized a (Y 1/4 Ho 1/4 Er 1/4 Yb 1/4 ) 2 SiO 5 ceramic with excellent phase stability and low thermal conductivity (1.1 W•m -1 •K -1 at 1300°C), which is considered to be applied as a thermal and environmental barrier coating (TEBC) material. Yan et al. 9 reported a high-entropy ceramic (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, which exhibited a much lower thermal conductivity (5.42-6.45 W•m -1 •K -1 at room temperature) than the binary carbides, such as HfC, ZrC, TaC, and TiC(6.3-29.3 W•m -1 •K -1 at room temperature). Zhao et al. 10 reported a new type of rare-earth zirconate (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 high-entropy ceramic with low thermal conductivity (0.76 W -1 •m -1 •k -1 ) and low grain growth speed, which consolidated its potential value in the field of TBCs. Zhao et al. 11 reported (Nd 0.2 Sm 0.2 Eu 0.2 Y 0.2 Yb 0.2 ) 4 Al 2 O 9 exhibits a close thermal expansion coefficient (6.96 × 10 −6 K −1 at 300-1473 K) to that of mullite, good phase stability from 300 to 1473 K, and low thermal conductivity (1.50 W -1 •m -1 •k -1 at room temperature).

First‐principles study of thermophysical properties of polymorphous YTaO4 ceramics

“…Moreover, pure RETaO 4 , RE 3 TaO 7 , and RETa 3 O 9 have been widely studied, and in order to optimize the thermal properties, doping (including Mg 2+ , 12 Al 3+ , 13 Zr 4+ , 14,15 and Nb 5+ 16-18 ) methods and defect engineering have been shown to be an effective and promising approach. 12,15,[19][20][21][22][23] The results showed that they had lower thermal conductivity and excellent TECs compared with 7-8YSZ. 19 In addition, relevant studies have revealed that RETaO 4 has a ferroelastic domain, 24 which enhances the fracture toughness of materials.…”

“…29,30 The physics of resin under pressure is similar to the seepage pr lar approaches have been used also to mod into a mold containing fiber mats. 23,[31][32][33][34][35][36][37][38] T in these cases to determine the resin flow ing times corresponding to different infilt Preceramic polycarbosilane polymers as precursors to make ceramic fibers 10,3 trix. [7][8][9]40,41 The chemical and volume ch pany ceramization of the polymer during documented in several studies.…”

“…Processes that have been modeled include RMI, 15,16 CVD, 17,18 CVI, [19][20][21][22] and Sol-Gel Infiltration. 23 Impregnation of alumina matrix in eight-harness satin Nextel 610 fabric has been studied numerically in Ref. [ 24 ].…”

“…29,30 The physics of resin flow into a mold under pressure is similar to the seepage problem and so similar approaches have been used also to model the flow of resin into a mold containing fiber mats. 23,[31][32][33][34][35][36][37][38] The models are used in these cases to determine the resin flow front and mold filling times corresponding to different infiltration conditions.…”

Experimental determination of the enthalpy of formation of the pyrochlore rare‐earth hafnates

“…Ceramics based on compounds of RE 2 O 3 -2HfO 2 type with pyrochlore structure are good candidates for TBC materials due to the possession of high strength characteristics, low thermal conductivity, and high melting temperatures. 1,2 The RE 2 O 3 -2HfO 2 ceramics, containing either one or several rare earths (high-entropy ceramics) are currently widely explored in terms of thermomechanical properties [3][4][5] and CMAS resistance. 6 Yet the thermodynamic properties of light rare-earth pyrochlore hafnates, important for the reliable phase diagram determination, are insufficiently studied.…”