Effect of physical vapor deposited Al2O3 film on TGO growth in YSZ/CoNiCrAlY coatings

Thermal barrier coatings (TBCs) comprising of yttria stabilized zirconia (YSZ) ceramic top coat and CoNiCrAlY metallic bond coat have been widely used in gas turbines. However, the developed oxides layer in the interface of the top and bond coats during thermal exposure of the TBCs always results in the destruction of the system. In order to restrain the growth of oxides layer and improve the thermal shock resistance of TBCs, a thin Al₂O₃ film was pre-deposited on CoNiCrAlY bond coat by physical vapor deposition (PVD) technology. After thermal exposure, morphologies and phase compositions of the thermal growth oxides (TGO) layer in the conventional and pre-deposited Al₂O₃ film TBCs were examined by scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). The residual stresses in the coatings were analyzed using micro-Raman spectroscopy (LabRam-1B). It was found that TGO layer formed in the conventional TBCs was mainly composed of Al₂O₃, (Cr,Al)₂O₃ + (Co,Ni)(Cr,Al)₂O₄ + NiO (CSN), and (Cr,Al)₂O₃ + (Co,Ni)(Cr,Al)₂O₄ (CS), while in the treated TBCs, the formed TGO layer appeared more uniform and compact. The CSN and CS clusters, which are normally considered as a weakness for TBCs, were greatly limited. The residual stresses in the TBCs after thermal shock were also reduced by the deposition of Al₂O₃ film.     

Evaluation of degradation of thermal barrier coatings using impedance spectroscopy

In this work, impedance spectroscopy (IS) has been used to evaluate the degradation of thermal barrier coatings (TBCs) due to oxidation at 1150^oC. The spallation of TBCs was found to be induced by the development of thermally grown oxides (TGO) produced from the oxidation of TBCs. The change in the electrical properties of the TGOs was found to be related to the change in the microstructure and microchemistry of the TGO. The resistivity of the TGO due to oxidation from 10 to 1000 h decreased rapidly, which corresponded to the increase in porosity in the TGO and the compositional change of the TGO from α-Al₂O₃ to a mixture of α-Cr₂O₃ and (Ni,Co)(Cr,Al)₂O₄ spinel. The slow decrease in the resistivity of the TGO from oxidation for 1000–2000 h indicated that there was little change in the composition of the mixed oxides, although the growth rate of the TGOs was relatively fast during this oxidation period. The disappearance of α-Al₂O₃ in the TGO caused a rapid oxide growth during oxidation and led to the spallation of TBCs.     

Thermal cycling behavior of nanostructured 8YSZ，SZ/8YSZ and 8CSZ/8YSZ thermal barrier coatings fabricated by atmospheric plasma spraying

The nanostructured single-ceramic-layer (SCL) 8YSZ thermal barrier coatings (TBCs), double-ceramic-layer (DCL) Sm₂Zr₂O₇ (SZ)/8YSZ and SZ doped with 8 wt% CeO₂ nanoscale particles (8CSZ)/8YSZ TBCs were fabricated by atmospheric plasma spraying (APS) on nickel-based superalloy substrates with NiCoCrAlY as the bond coating. The thermal cycling behavior of the three as-sprayed TBCs was investigated systematically at 1000 ℃ and 1200 ℃. The results reveal that the thermal cycling lifetime of the nanostructured DCL 8CSZ/8YSZ TBCs is the longest among them, which is largely due to the fact that the intermediate layer buffer effect of the DCL structure, more porosity and improvement of thermal expansion coefficient from doping CeO₂ nanoparticles can relieve thermal stress to a great extent at elevated temperature. The failure mechanism of the nanostructured TBCs has been discussed in detail.     

Microstructure evolution of Al-modified 7YSZ PS-PVD TBCs in thermal cycle

The PS-PVD method was used to prepare 7YSZ thermal barrier coatings (TBCs) and NiCrAlY bond coatings on a DZ40 M substrate. To prevent oxidation of the coating, magnetron sputtering was used to modify the surface of TBCs with an Al film. To explore the stability of TBCs during thermal cycling, water quenching was performed at 1100 °C, and ultralong air cooling for 16,000 cycles was performed. The results showed that before water quenching and air cooling, the top surface structure of the 7YSZ TBCs changed. After water quenching, the surface of the Al film was scoured and broken, the surface peeled off layer-by-layer, and cracks formed at the interface between the thermally grown oxide and NiCrAlY. During air cooling of the thermal cycle, the Al film reacted with O₂ in the air to form a dense Al₂O₃ top layer that coated the cauliflower-like 7YSZ surface and maintained the feather-like shape. At the same time, the TGO layer between 7YSZ and NiCrAlY grew and cracked. The two thermal cycles of water quenching and air cooling led to different failure mechanisms of TBCs. Water quenching failure was caused by layer-by-layer failure of the 7YSZ top coat, while air cooling failure occurred due to the internal cracking of the TGO layer at the 7YSZ/NiCrAlY interface and the failure of the TGO/NiCrAlY interface.     

Methane Oxidation Over M–8YSZ and M–CeO2/8YSZ (M = Ni, Cu, Co, Ag) Catalysts

The oxidation of methane has been studied by sequential flow reaction experiments over M–8YSZ and M–CeO₂/8YSZ (M=Ni, Cu, Co, Ag) catalysts as a function of CH₄/O₂ from 773 to 1073 K. Over Ni–8YSZ and Ni–CeO₂/8YSZ, methane pyrolysis is dominant leading to surface carbon formation at temperatures of 873 K and above. While the addition of ceria to Ni–8YSZ to produce Ni–CeO₂/8YSZ does not significantly affect the reaction kinetics, the activity of Cu–CeO₂/8YSZ, Co–CeO₂/8YSZ, and Ag–CeO₂/8YSZ are higher than their M–8YSZ counterparts. The activity of Co–CeO₂/8YSZ at high temperatures (973 K and above) is higher than Ni-8YSZ with selectivity towards partial methane oxidation and CO formation. Considering Ni-based catalysts are prone to deactivation due to surface carbon accumulation, Co–CeO₂/8YSZ, Cu–CeO₂/8YSZ, and Ag–CeO₂/8YSZ are possible alternative anode cermets for direct hydrocarbon oxidation solid-oxide fuel cells (SOFC).     

Effect of TGO Thickness on Thermal Cyclic Lifetime and Failure Mode of Plasma‐Sprayed TBCs

Gradient thermal cycling test was performed on atmospheric plasma‐sprayed (APS) thermal barrier coatings (TBCs) with different thermally grown oxide (TGO) thicknesses. The TBCs with a thickness of TGO from 1.3 μm to 7.7 μm were prepared by controlling isothermal oxidation time of cold‐sprayed MCrAlY bond coat. The gradient thermal cycling test was performed at a peak surface temperature of 1150°C with 150°C difference across 250 μm thick YSZ with a duration of 240 s for each cycle. Results indicate that the thermal cyclic lifetime of APS TBCs is significantly influenced by TGO thickness. When initial TGO thickness increases from 1.3 μm to 7.7 μm, the thermal cyclic lifetime decreases following a power functions by a factor of about 20. It was revealed that there exists a critical TGO thickness over which the thermal cyclic lifetime is reduced more significantly with the increase in TGO thickness. Moreover, two typical failure modes were observed. The failure mode changes from the cracking within APS YSZ at a TGO thickness less than the critical value to through YSZ/TGO interface at TGO thickness range higher than the critical value.     

Performance of mix‐impregnated CeO2‐Ni/YSZ Anodes for Direct Oxidation of Methane in Solid Oxide Fuel Cells

CeO₂‐Ni/YSZ anodes for methane direct oxidation were prepared by the vacuum mix‐impregnation method. By this method, NiO and CeO₂ are obtained from nitrate decomposition and high temperature sintering is avoided, which is different from the preparation of conventional Ni‐yttria‐stabilised zirconia(YSZ) anodes. Impregnating CeO₂ into the anode can improve the cell performance, especially, when CH₄ is used as fuel_. The investigation indicated that CeO₂‐Ni/YSZ anodes calcined at higher temperature exhibited better stability than those calcined at lower temperature. Under the testing temperature of 1,073 K, the anode calcined at 1,073 K exhibited the best performance. The maximum power density of a cell with a 10 wt.‐%CeO₂‐25 wt.‐%Ni anode calcined at 1,073 K reached 480 mW cm^–2 after running on CH₄ for 5 h. At the same time, high discharge current favoured cell operation on CH₄ when using these anodes. No obvious carbon was found on the CeO₂‐Ni anode after testing in CH₄ as revealed from SEM and corresponding linear EDS analysis. In addition, cell performance decreased at the beginning of discharge testing which was attributed to the anode microstructure change observed with SEM.     

Gradient thermal cycling behavior of a thermal barrier coating system constituted by NiCoCrAlY bond coat and pure metastable tetragonal nano-4YSZ top coat

Pure metastable tetragonal (t’) phase 4YSZ top coats with thickness of 100 and 200 μm were deposited on NiCoCrAlY-coated second generation single crystal superalloy by air plasma spray (APS). The two thermal barrier coatings were evaluated under gradient thermal cycling test using gas mixture of propane and oxygen. After flame shock test, the values of Young's modulus, hardness and degree of densification all exhibited a gradient distribution across YSZ thickness. In contrast to intensive sintering at surface of 200 μm 4YSZ coating, the TBC sample with 4YSZ layer of 100 μm underwent poor oxidation at interface of YSZ and bond coat, forming a duplex oxide scale: (Ni,Co)(Cr,Al)₂O₄ spinel over Al₂O₃, which promoted the delamination at the top-coat/bond-coat interface. The resistance against gradient thermal cycling, the phase stability of 4YSZ and the failure mechanism of the TBCs, were discussed correlating to the effects of YSZ thickness.     

Isothermal oxidation and TGO growth behaviors of YAG/YSZ double-ceramic-layer thermal barrier coatings

In this study, yttrium aluminum garnet/yttria-stabilized zirconia (YAG/YSZ) double-ceramic-layer thermal barrier coatings (DCL TBC) and yttria-stabilized zirconia (YSZ) single-ceramic-layer thermal barrier coatings (SCL TBC) were deposited by atmosphere plasma spray (APS) on the Inconel 738 alloy substrate, and isothermal oxidation tests were performed to investigate the formation and growth behavior of thermally grown oxide (TGO). Results showed that the Al₂O₃ TGO thickness of both TBC groups increased by increasing the isothermal oxidation time，and then slowly decreased with the appearance and growth of the adverse multilayer structure comprising CoCr₂O₄, (Ni,Co)Al₂O₄, NiCr₂O₄, and NiO mixed oxides. However, since the significant inhibition effect of the YAG coating to oxygen ionic diffusion, the mixed oxides appearance time and TGO growth behaviors were delayed in the DCL TBC. As a result, the TGO thickness of the DCL TBC was always smaller than that of the SCL TBC in the entire oxidation process. And the Al₂O₃ layer thickness proportion in the total TGO of the DCL TBC was greater than or equal to that of the SCL TBC after oxidation for the same period. The results of weight gain showed that compared with the SCL TBC, the parabolic oxidation rate of the DCL TBC was decreased approximately 35%. Consequently, the DCL TBC has better high-temperature oxidation resistance than the SCL TBC.     

Study of Carbon Deposition Behavior on Cu–Co/CeO2–YSZ Anodes for Direct Butane Solid Oxide Fuel Cells

Electro‐catalytic activity of Cu–Co/CeO₂–YSZ anodes towards oxidation of H₂ and n‐C₄H₁₀ fuels and carbon depositions are investigated using different Cu–Co loadings. Cu–Co/CeO₂–YSZ anode based SOFCs with YSZ as electrolyte and LSM/YSZ as cathode were prepared by tape casting and wet impregnation methods and performance was analyzed using I–V characteristics and impedance spectroscopy. The Cu–Co/CeO₂–YSZ anodes with Cu–Co loading of 10, 15, and 25 wt.% produced power density of 60, 197, and 400 mW cm^–2 in H₂ and 190, 225, and 275 mW cm^–2 in n‐C₄H₁₀ at 800 °C. The power density is increased with the increase in Cu–Co loading in Cu–Co/CeO₂–YSZ anodes. The electrochemical impedance spectra shows less ohmic and polarization resistance for 25 wt.% Cu–Co loading in comparison to 10 and 15 wt.% Cu–Co. Scanning electron microscopy and high resolution transmission electron microscopy shows that the carbon fibers formed are hollow in nature with 70 nm size, whereas, thermal gravimetric analysis and X‐ray diffraction points out that they are amorphous in nature. The performance degradation of Cu–Co/CeO₂–YSZ anodes in n‐C₄H₁₀ in 16 h is attributed to increasing amount of carbon deposition with time, which is contrary to our earlier observation in Cu‐Fe/CeO₂–YSZ anode.     

Thermochemical compatibility between La2(Ce1-xZrx)2O7 and 4 mol% Y2O3 stabilized zirconia after high temperature heat treatment

La₂Ce₂O₇ (LC) has attracted extensive attention as promising material for thermal barrier coatings (TBCs) in next generation gas turbines due to its outstanding thermophysical properties. To eliminate the reaction between LC and thermal grown oxides (TGO), yttria stabilized zirconia (YSZ) is usually employed as the interlayer to form LC/YSZ double-layered structures. However, recent studies have revealed that chemical stability of LC and YSZ system deteriorates at high temperatures, which may hinder the application of LC as TBCs. To address this problem, the chemical compatibility between La₂(Ce_1-xZr_x)₂O₇ (LCZ) and YSZ at high temperatures was investigated in this work via experiments and atomistic simulations. Results reveal that chemical compatibility increased with the increase in Zr content of LCZ. Corresponding molecular dynamic simulations further verify that the increase in Zr content of LCZ system would reduce Gibbs free energy of LCZ-YSZ composite system. Moreover, common phenomena in LC-YSZ system, such as abnormal grain coarsening and intensive pore diffusion, were effectively suppressed in LCZ-YSZ composite, due to enhanced high temperature chemical compatibility. Results also indicate that the addition of buffer layer, i.e., LCZ-YSZ composite, can effectively improve chemical stability of TBCs based on double layered LC/YSZ.     

Comparative study on effect of oxide thickness on stress distribution of traditional and nanostructured zirconia coating systems

Numerical based assessment of traditional and nanostructured yttria stabilized zirconia (YSZ) thermal barrier coating systems (TBCs) has been carried out with varying thickness of thermally grown oxide (TGO). Radial, axial and shear stresses are determined for both coatings and are presented in comparison with few novel and interesting results. Elastic strain energy for TGO failure assessment is determined from calculated stress within TGO for varying thickness. Radial stresses at TGO/bond coat interface and maximum axial stresses in nanostructured zirconia coatings are found to be lower than in traditional YSZ up to a critical TGO thickness of 6 –7 μm, after which stresses in nanostructured zirconia coatings increase considerably. However, radial compressive stresses in nanostructured TBCs are lower in all TGO thickness cases and shear stresses are slightly higher with relatively more prominent difference at high oxide thickness.     

Studies on nanotribological and oxidation resistance properties of yttria stabilized zirconia (YSZ), alumina (Al2O3) based thin films developed by pulsed laser deposition

The present study aims at a detailed evaluation of mechanical, tribological, and high temperature oxidation resistance (at 1000 °C under isothermal condition) properties of YSZ, and Al₂O₃ based thin films developed by pulsed laser deposition technique. The mechanical and tribological properties of YSZ and Al₂O₃ thin films showed significant improvement with increasing the deposition temperature during pulsed laser deposition process. The kinetics of oxidation was reduced due to pulsed laser deposition and Al₂O₃ coating offered a superior oxidation resistance property as compared to YSZ coating. However, the deposition temperature has no significant effect in reducing the TGO growth rate of the pulsed laser deposited thin films.     

Phase stability,thermo-physical properties and thermal cycling behavior of plasma-sprayed CTZ,CTZ/YSZ thermal barrier coatings

ZrO₂ co-stabilized by CeO₂ and TiO₂ with stable, nontransformable tetragonal phase has attracted much attention as a potential material for thermal barrier coatings (TBCs) applied at temperatures >?1200?°C. In this study, ZrO₂ co-stabilized by 15?mol% CeO₂ and 5?mol% TiO₂ (CTZ) and CTZ/YSZ (zirconia stabilized by 7.4?wt% Y₂O₃) double-ceramic-layer TBCs were respectively deposited by atmospheric plasma spraying. The microstructures, phase stability and thermo-physical properties of the CTZ coating were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric-differential scanning calorimeter (TG-DSC), laser pulses and dilatometry. Results showed that the CTZ coating with single tetragonal phase was more stable than the YSZ coating during isothermal heat-treatment at 1300?°C. The CTZ coating had a lower thermal conductivity than that of YSZ coating, decreasing from 0.89?W?m^?1 K^?1 to 0.76?W?m^?1 K^?1 with increasing temperature from room temperature to 1000?°C. The thermal expansion coefficients were in the range of 8.98?×?10^?6 K^?1 – 9.88 ×10^?6 K^?1. Samples were also thermally cycled at 1000?°C and 1100?°C. Failure of the TBCs was mainly a result of the thermal expansion mismatch between CTZ coating and superallloy substrate, the severe coating sintering and the reduction-oxidation of cerium oxide. The thermal durability of the TBCs at 1000?°C can be effectively enhanced by using a YSZ buffer layer, while the thermal cycling life of CTZ/YSZ double-ceramic-layer TBCs at 1100?°C was still unsatisfying. The thermal shock resistance of the CTZ coating should be improved; otherwise the promising properties of CTZ could not be transferred to a well-functioning coating.     

Effects of shot peening on microstructure,thermal performance,and failure mechanism of thermal barrier coatings

Shot peening might be a potential technology to optimize the interface microstructure, plays a critical role on failure behaviors, of thermal barrier coatings (TBCs). It remains a significant challenge to understand the influence of shot peening on microstructure, oxidation resistance, and thermal shock life. In this work, the Y₂O₃-stabilized ZrO₂ TBCs have been deposited by EB-PVD. The phase, microstructure, thermal performance, and failure mechanism of TBCs have been systemically investigated after shot peening. The shot peening process can improve the planeness of interface and reduce the formation of the cauliflower-liked microstructure in TBCs. After shot peening, the TBC coatings exhibit relatively good isothermal oxidation resistance and high thermal shock life due to the optimization of TGO growth and the thermal stability. The phase transformation, TGO growth, and cracks extension might give rise to the failure of TBCs. This work might guide the investigation of the improvement of interface microstructure and failure behaviors.     

Thermal cycling failure of the multilayer thermal barrier coatings based on LaMgAl11O19/YSZ

Thermal cycling failure of three multilayer TBCs based on LaMgAl₁₁O₁₉ (LaMA)/YSZ was comparatively investigated by using the burner-rig testing method in this work. Results indicate that through optimizing the weight ratio and thickness of the intermediate LaMA/YSZ composite layers, a five-layer TBC with much improved thermal cycling life of 11,749 cycles at 1372 °C surface and 1042 °C bond coat testing temperature has been realized. While, thermal cycling lifetimes of the tri- and six-layer TBCs were 7439 and 7804 cycles at surface/bond coat testing temperatures of 1378 °C/1065 °C and 1367 °C/1056 °C, respectively. Factors related to the 60 wt.% LaMA + 40 wt.% YSZ (60LaMA + 40YSZ) intermediate composite layer with the highest thermal expansion coefficient than other composite layers generating higher internal stress level to the tri- and six-layer TBCs, different bond coat temperature and TGO growth, as well as long-term stability of the LaMA coating during thermal cycling tests, were characterized and compared to understand the different thermal cycling lifetime and failure modes among such three multilayer TBCs.     

Thermal shock behavior of 8YSZ and double-ceramic-layer La2Zr2O7/8YSZ thermal barrier coatings fabricated by atmospheric plasma spraying

The single-ceramic-layer (SCL) 8YSZ (conventional and nanostructured 8YSZ) and double-ceramic-layer (DCL) La₂Zr₂O₇ (LZ)/8YSZ thermal barrier coatings (TBCs) were fabricated by plasma spraying on nickel-based superalloy substrates with NiCrAlY as the bond coat. The thermal shock behavior of the three as-sprayed TBCs at 1000 °C and 1200 °C was investigated. The results indicate that the thermal cycling lifetime of LZ/8YSZ TBCs is longer than that of SCL 8YSZ TBCs due to the fact that the DCL LZ/8YSZ TBCs further enhance the thermal insulation effect, improve the sintering resistance ability and relieve the thermal mismatch between the ceramic layer and the metallic layer at high temperature. The nanostructured 8YSZ has higher thermal shock resistance ability than that of the conventional 8YSZ TBC which is attributed to the lower tensile stress in plane and higher fracture toughness of the nanostructured 8YSZ layer. The pre-existed cracks in the surface propagate toward the interface vertically under the thermal activation. The nucleation and growth of the horizontal crack along the interface eventually lead to the failure of the coating. The crack propagation modes have been established, and the failure patterns of the three as-sprayed coatings during thermal shock have been discussed in detail.     

Low–thermal–conductivity and high–toughness CeO2–Gd2O3 co–stabilized zirconia ceramic for potential thermal barrier coating applications

Yttria partially stabilized zirconia (～4.0?mol% Y₂O₃–ZrO₂, 4YSZ) has been widely employed as thermal barrier coatings (TBCs) to protect the high–temperature components of gas–turbine engines. The phase stability problem existing in the conventional 4YSZ has limited it to application below 1200?°C. Here we report an excellent zirconia system co–doped with 16?mol% CeO₂ and 4?mol% Gd₂O₃ (16Ce–4Gd) presenting nontransformable feature up to 1500?°C, in which no detrimental monoclinic (m) ZrO₂ phase formed on partitioning. It also exhibits a high fracture toughness of ～46?J m^?2 and shows high sintering resistance. Besides, the thermal conductivity and thermal expansion coefficient of 16Ce–4Gd are more competent for TBCs applications as compared to the 4YSZ. The combination of properties suggests that the 16Ce–4Gd system could be of potential use as a thermal barrier coating at 1500?°C.     

Finite element analysis of TGO thickness on stress distribution and evolution of 8YSZ thermal barrier coatings

According to the experimental research results of the thermally grown oxide (TGO) layered growth during the pre-oxidation process of 8 wt.% yttria-stabilized zirconia thermal barrier coating (TBC), a two-dimensional sinusoidal TC/bonding coat (BC) curve interface model of the longitudinal section of TBCs based on finite element simulation was constructed; the thickness and composition of the TGO layer relative to the TC/BC curve interfacial stress distribution and its evolution during the thermal cycling process were studied. The results show that when the TGO layer uses α-Al₂O₃ as the main oxide (black TGO), the thicker the black TGO layer, the more uniform the stress distribution of the TC/BC interface. When the TGO layer is dominated by spinel-structured Co and Cr oxides (gray TGO), the stress “band” of the TC/BC interface is destroyed; it shows the alternating phenomenon of tensile stress zone and compressive stress zone, and after the rapid random growth of TGO, the concentrated tensile stress increased by a large jump. Affected by the thickness of the prefabricated black TGO layer, there is a limit peak in the thickness of the black TGO layer, the normal stress at the TC/BC boundary is minimized, and the magnitude of the stress change is also minimized.     

Evaluation of mechanical properties of YSZ TBCs doped by different ratios of Eu3+ ions after isothermal oxidation

Thermal barrier coatings (TBCs) are essential to improve the thermal insulation performance of high-temperature components. Rare earth element (Eu³⁺) doped yttrium stabilized zirconia (YSZ) TBCs have been proved to be an ideal solution for non-destructive testing of internal damages. Based on this theory, two types of coatings deposited by air plasma spray (APS) on Hastelloy-X were investigated: (1) Eu³⁺ doped YSZ (dopant ratios 1 mol%, 2 mol%, 4 mol%, respectively), (2) traditional undoped 8YSZ. Isothermal oxidation treatment at 1100 °C, in increments of 10h until the failure of the coatings are conducted to evaluate the mechanical properties of different coatings. The microscopic morphology and phase of the coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) patterns, respectively. The indentation testing methods were used to study the apparent interfacial fracture toughness and the hardness of the ceramic top coat. Results show that the Vickers hardness of the top coat increases with the decrease of porosity in the early stage and then decreases with the heat treatment time increasing in the long-term stage. Simultaneously, compared with the undoped 8YSZ coating, the fracture toughness increased with the dopant of Eu³⁺ ions increasing, from 1 mol% to 2 mol%, nevertheless, that of 4 mol% Eu³⁺ doped YSZ decreased compared with in the undoped 8 YSZ. For all types of specimens, the interfacial fracture toughness decreases with the increase of isothermal oxidation time. Results also indicate that the content of Eu³⁺ doping does not affect the microstructure and interfacial morphology of the YSZ coating as well as the growth law of thermally grown oxides (TGO). Furthermore, EDS detection found that the Eu³⁺ ions almost do not diffuse inside the TBCs system after isothermal oxidation treatment.