Optimization thermophysical properties of TiO₂ alloying Sm₃TaO₇ ceramics as promising thermal barrier coatings

Abstract

TiO2 alloying effect is applied to optimize the thermophysical properties of fluorite‐type Sm3TaO7 ceramics synthesized via solid‐state reaction, and the influence of TiO2 alloying effect on the optical properties and elastic modulus is determined. According to the decreasing unit cell volume calculated by the X‐ray diffraction and the broadening Raman peak, Ti4+ substitutes the same number of Sm3+ and Ta5+ ions of Sm3TaO7 ceramics at the same time. As Ti4+ substitutes Sm3+ and Ta5+ ions, the band gap of TiO2‐Sm3TaO7 ceramics decreases from 4.71 to 4.11 eV. The phase transition of Sm3TaO7 ceramics is eliminated by TiO2 alloying effect and the coefficient of thermal expansion is increased. Via TiO2 alloying effect, two different phonon scattering mechanisms: (a) the misfit of atomic weight and ionic radius among Ti4+, Sm3+, and Ta5+ ions; (b) the rattling Ti4+ ions are introduced in Sm3TaO7 ceramics. The lowest thermal conductivity of TiO2‐Sm3TaO7 ceramics reaches 1.37 W K−1 m−1 (800°C, 9 mol% TiO2‐Sm3TaO7), which is much lower than 7YSZ and Sm2Zr2O7 ceramics. Accordingly, it is believed that TiO2‐Sm3TaO7 ceramics are promising thermal barrier coatings.

High entropy defective fluorite structured rare-earth niobates and tantalates for thermal barrier applications

“…Nevertheless, previous studies indicate that the mechanical properties of RE 3 TaO 7 and RE 3 NbO 7 , such as Vickers hardness, are significantly lower than those of YSZ [17,[22][23][24]. Moreover, some compounds such as Sm 3 TaO 7 and Sm 3 NbO 7 exhibit phase transition with an abrupt volume change at 942 and 817 ℃, respectively, which is unfavorable to their application as TBC materials [22,25].…”

Influence of HfO2 alloying effect on microstructure and thermal conductivity of HoTaO4 ceramics

“…When Ho 3+ is substituted by Hf 4+ , the crystal structure will be contracted, and the XRD peaks shift to right. Figure 1(b) indicates that the 2-theta position of main XRD peaks of HfO 2 -HoTaO 4 is constant; therefore, it is believed that the same numbers of Ho 3+ and Ta 5+ ions are substituted by Hf 4+ cations [19,24]. A weak peak of HfO 2 is found in 9 mol%-HfO 2 HoTaO 4 , which can be observed more distinctly from Fig.…”

“…To promote the material property of rare earth tantalates further, many methods have been tried. For example, TiO 2 and ZrO 2 alloying effects are employed to produce glass-like thermal conductivity; Al 2 O 3 doping is utilized to drop thermal conductivity and enhance thermal expansion coefficients (TECs) [19,24,25]. Among various technologies, alloying effect is considered as the most effective one, as the TECs and thermal conductivity are simultaneously optimized.…”

Investigation of thermophysical properties of ZrO2-Sm3TaO7 ceramics

“…All the ceramic data showed good linearity, except for those for 2 mol% ZrO 2 doping, caused by a phase transition. According to previous research on TiO 2 -Sm 3 TaO 7 ceramics [22], the phase transition of Sm 3 TaO 7 ceramics is eliminated via the TiO 2 alloying effect. The TEC of the samples increased with increasing temperature and ZrO 2 content, as shown in Figure 8(b).…”

“…La 3 TaO 7 and Nd 3 TaO 7 ceramics exhibited an increase in thermal conductivity above 600°C. The minimum thermal conductivities of Y 3 TaO 7 [20] and ZrO 2 -Eu 3 TaO 7 [21] [22,23]. Because of the unique properties of Sm [24], the application temperature of Sm 2 Zr 2 O 7 ceramics as TBCs exceeds 1500°C.…”