Thermal Barrier Coatings Based on ZrO2 Solid Solutions

• Published in: Powder metallurgy and metal ceramics Vol. 59; no. 3-4; pp. 179 - 200
• Main Authors: Dudnik, E.V., Lakiza, S.N., Hrechanyuk, I.N., Ruban, A.K., Redko, V.P., Marek, I.O., Shmibelsky, V.B., Makudera, A.A., Hrechanyuk, N.I.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.07.2020; Springer Nature B.V
• Subjects: Ceramic coatings; Ceramics; Cerium oxides; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Erbium oxide; Fatigue life; Fracture toughness; Gadolinium oxides; Gas turbine engines; Glass; Heat conductivity; Heat transfer; High temperature; Lanthanum oxides; Materials Science; Metallic Materials; Natural Materials; Operating temperature; Phase stability; Protective and Functional Powder Coatings; Rare earth elements; Scandium oxides; Solid solutions; Tantalum; Tantalum oxides; Temperature; Thermal barrier coatings; Thermal conductivity; Thermal fatigue; Thermal resistance; Titanium dioxide; Titanium oxides; Yttria-stabilized zirconia; solid solution; titanium oxide; ZrO; complex doping; zirconia; thermal barrier coatings; rare-earth metal oxides
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-020-00151-8

The standard material of the ceramic layer in thermal barrier coatings (TBCs)—a solid solution of ZrO 2 stabilized with (6–8 wt.%) Y 2 O 3 (YSZ)—approaches the temperature limit of its application (<1200°C) because the ZrO 2 t′ phase sinters and undergoes t′-ZrO 2 → T-ZrO 2 + F-ZrO 2 phase transformations to form M-ZrO 2 at elevated temperatures. Ceramic materials for a new generation of TBCs need to be developed to increase the operating temperature (up to 1600°C), efficiency, and productivity of gas-turbine engines. The overview paper analyzes research efforts focusing on the development of TBCs using solid solutions of ZrO 2 with rare-earth metal and titanium oxides. When Y 2 O 3 in YSZ is partially substituted by CeO 2 , TiO 2 , La 2 O 3 , Sc 2 O 3 , Gd 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Er 2 O 3 , and Ta 2 O 5 , ceramics with high phase stability (ZrO 2 t′ phase being retained in the coating) up to 1500°C, lower thermal conductivity, and required fracture toughness and sintering resistance but shorter thermal fatigue life than that of standard YSZ are produced. The concepts of greater tetragonality of the ZrO 2 t′ phase (ceramics in the ZrO 2 –CeO 2 –TiO 2 system) and a ‘multicomponent defective cluster’ (ceramics in the ZrO 2 –Y 2 O 3 –Nd 2 O 3 (Gd 2 O 3 , Sm 2 O 3 )–Yb 2 O 3 (Sc 2 O 3 ) system) explain how the operating temperature of the TBC ceramic layer increases to 1350°C and 1600°C, respectively. The thermal conductivity of TBC ceramics in the binary ZrO 2 –CeO 2 , ZrO 2 –Er 2 O 3 , ZrO 2 –Sm 2 O 3 , ZrO 2 –Nd 2 O 3 , ZrO 2 –Gd 2 O 3 , ZrO 2 –Dy 2 O 3 , and ZrO 2 –Yb 2 O 3 systems is lower than that of YSZ. Ceramics with high phase stability and low thermal conductivity have been produced in the ternary ZrO 2 –Sc 2 O 3 –Gd 2 O 3 , ZrO 2 –CeO 2 –Gd 2 O 3 , ZrO 2 –YbO 1.5 –TaO 2.5 , and ZrO 2 –Yb 2 O 3 –TiO 2 systems. An integrated approach is needed to choose the composition of the ceramic layer based on the ZrO 2 solid solution, select the coating technique, and improve the coating architecture to design effective TBCs with balanced properties.