## 1 Introduction  
Thermal barrier coatings (TBCs) are a protective coating widely employed in the hot-section components of aero-engines. It is usually a functional coating composed of bonding and top ceramic layers [1]. The bonding layer is mainly prepared by NiCrAIY and other metal powders, which is employed to connect the high-temperature alloy substrate and the ceramic layer, and reduces the thermal stress caused by the thermal expansion mismatch between the high-temperature substrate and the ceramic layer. Owing to its special material properties, the top ceramic layer has low thermal conductivity and high thermal insulation performance, which provides thermal insulation protection for the superalloy substrate [2; 3]. The use of a thermal barrier coating system improves the working temperature and efficiency of aero-engine hot-section components. At present, the thermal barrier coating technology is listed as one of the three key technologies for the design of high-performance aero-engine hot-section components with high-temperature structural materials and high-efficiency blade cooling technology in the aero-engine propulsion plans of the United States, Europe, and China, which is crucial to the development of the aviation industry [4; 5]. In the process of preparing thermal barrier coatings, the most critical thing is to spray and deposit the ceramic layer and the bonding layer onto the protected superalloy substrate. Different preparation processes have a great effect on the performance and life of TBCs [6; 7]. To improve the service life of TBCs, experts and scholars have developed a variety of TBCs preparation processes, such as plasma spraying, suspension plasma spraying, etc. [8; 9; 10]. At present, among the methods for preparing TBCs, atmospheric plasma spraying (APS) has become one of the most widely employed methods for preparing TBCs owing to its low manufacturing cost, high deposition efficiency, and large adjustment range of coating thickness [11]. In the process of APS, the spraying material is sent to the high-temperature (center temperature 2 \(\times\) 10\({}^{4}\) K) flame flow and heated to the molten state. The molten droplets are driven by the flame flow to impact the surface of the alloy substrate at a high speed (about 1 Mach) to expand into flat particles and rapidly solidify. Finally, a layered structure composed of a large number of deformed lamellar particles is formed, and there are a large number of two-dimensional pores between the layers [12; 13]. Owing to the two-dimensional pores between the layers, TBCs have high thermal insulation performance and strain tolerance. High strain tolerance can alleviate the thermal stress caused by a long-term high temperature environment, reduce the cracks in the coating under a high-temperature service environment, and improve the service performance of the coating. However, the two-dimensional pores in the ceramic layer will heal during high-temperature service, resulting in sintering. The sintering phenomenon of the ceramic layer will significantly affect the strain tolerance and fracture toughness of TBCs, resulting in a gradual increase in the crack-driving force during the high-temperature thermal cycle, resulting in the cracking failure of TBCs. Once TBCs crack and fail, it will seriously affect the safety of aero-turbine engines [14; 15; 16; 17]. Therefore, to ensure the safe use of the aero-engine and prolong the service life of TBCs, it is necessary to improve the sintering resistance of the ceramic layer. The sintering resistance of the ceramic layer is one of the main properties of TBCs. Scholars have developed various strategies to improve the sintering resistance of the ceramic layer. Scholars have improved the microstructure of the coating by changing the preparation process of plasma spraying, thereby improving the sintering resistance of the coating. [PERSON] et al. used special APS equipment to prepare TBCs with vertical cracks, which greatly improved the service life of the coating [18]. [PERSON] et al.