Yb₂O₃‐Gd₂O₃ codoped strontium zirconate composite ceramics for potential thermal barrier coating applications

Abstract

Strontium zirconate (SrZrO3) has been considered as a promising thermal barrier coating (TBC) material for application in gas turbine engines; however, the phase transition problem limits its application. In this study, an Yb2O3 and Gd2O3 codoped SrZrO3 system with excellent properties was reported. Yb2O3‐Gd2O3 codoped SrZrO3 ceramic powders [Sr0.8(Zr0.9Yb0.05Gd0.05)O2.75, SZYG/YGZO], [Sr(Zr0.9Yb0.05Gd0.05)O2.95, SZYG] and pure SrZrO3 (SZO) powders were produced by a conventional solid‐state reaction method. The XRD and Raman results show that, the composite SZYG/YGZO ceramics consist of the SZO and Yb0.5Zr0.5O1.75 phases with a low thermal conductivity of ~1.3 W/(m·K) at 1000°C, which is at least 40% lower than that of the SZO ceramics. The TG‐DSC results show that the SZYG/YGZO ceramics have no phase transition in the temperature range of 600 to 1400°C. The thermal expansion coefficient of the SZYG/YGZO ceramics reaches 10.9 × 10−6 K−1 (1250°C). In addition, the fracture toughness of the SZYG/YGZO ceramics increases by more than 30% compared with the SZO ceramics, and this can be attributed to the presence of the Yb0.5Zr0.5O1.75 phase.

A new type of Sr(Zr0.2Hf0.2Ce0.2Yb0.2Me0.2)O3−x (Me = Y, Gd) high‐entropy ceramics used in thermal barrier coatings

“…Therefore, after a long time of heat treatment at 1400 • C, the material gradually transforms to a more stable structure, causing the B-site elements (Yb 3+ , Y 3+ , Gd 3+ ) precipitated in the ceramic as a secondary phases (AB 2 O 4 solid solution). 19 With an increase of annealing time, the relative contents of the second phase have increased gradually, but no new phase is formed.…”

“…However, the operating temperature of YSZ coating is generally limited to less than 1200 • C because of the phase transformation and coating sintering at high temperature. [18][19][20] Therefore, in order to meet the requirements of turbine blades for higher operating temperatures, more and more researchers have focused on the development of new TBCs materials with ultrahigh temperature stability and high thermal insulation. 21 Perovskites are usually characterized by high melting point, low thermal conductivity, and high thermal expansion coefficient (TEC), which have been considered potential TBCs materials.…”

Microstructure and Properties of Densified Gd2O3 Bulk

“…The Yb 2 O 3 -Gd 2 O 3 co-doped YSZ coating has a relatively low thermal conductivity of 1.1 W/(m·K) (at 1100 °C). Zhang et al [ 28 ] prepared Yb 2 O 3 and Gd 2 O 3 co-doped SrZrO 3 system with good properties through a traditional solid-state reaction. The SZYG/YGZO composite ceramics with Yb 0.5 Zr 0.5 O 1.75 and SZO phases possessed a thermal conductivity of 1.3 W/(m·K) (at 1000 °C), which was 40% less than the SZO ceramics’ at least.…”

“…However, how does the added Gd 2 O 3 enhance the material properties used in TBCs? This requires the properties of the pure Gd 2 O 3 , while there are few reports on the properties of Gd 2 O 3 [ 19 , 20 , 21 , 22 , 23 , 25 , 26 , 27 , 28 , 29 ]. By consulting the relevant literature [ 19 , 21 , 22 , 29 ], it can be found that there are no detailed values for the thermal physical properties, including the thermal conductivity and thermal expansion coefficient, as well as mechanical properties, including elastic modulus, hardness and fracture toughness of the pure Gd 2 O 3 .…”

Effect of Gd2O3 Addition on the Microstructure and Properties of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) Ceramics

“…Oxide co-dopped yttria stabilized zirconia ceramic material can change the structure of the thermal barrier coating system to make it a stable structure. In addition, Gd and Yb elements have a strong adsorption capacity for other elements, high chemical stability, and can be dissolved in a limited solid solution of ZrO 2 [ 27 , 28 , 29 , 30 ]. Therefore, the addition of Gd and Yb elements may greatly improve the performance of ZrO 2 thermal barrier coatings.…”