目的 热障涂层高温服役过程中产生的残余应力是导致其失效的关键因素,开发高灵敏度的无损检测技术对于评估涂层可靠性至关重要。本研究通过构筑不同体系耐高温YAG:xCe荧光应力响应单元提高热障涂层残余应力检测灵敏度。方法 采用真空烧结法构筑了不同浓度Ce3+掺杂的 Y3Al5O12（YAG:xCe,x=0.03、0.06、0.08、0.12）荧光应力响应单元复合粉末。利用大气等离子喷涂将所获得的复合粉末制备成系列YAG:xCe热障涂层陶瓷层。研究Ce3+掺杂浓度对复合粉末及涂层荧光性能的影响,通过密度泛函理论计算研究了不同Ce3+掺杂浓度与荧光应力之间的关系。结果 所制备的系列YAG:xCe涂层具有良好的高温稳定性,涂层荧光强度随 Ce3+掺杂浓度呈先增大后减小趋势,浓度为0.08%时,对应最大荧光峰位移。结论 成功构筑了系列YAG:xCe荧光应力响应单元,并明确了其发光效率与应力响应特性可通过掺杂浓度进行有效调控;阐明了掺杂浓度-晶格微变-荧光压谱效应之间的构效关系,为实现热障涂层内部应力状态的高灵敏、无损原位监测提供了重要的材料体系与理论依据,对新一代航空发动机热障涂层的健康监测与寿命预测具有积极的支撑作用。
Abstract
Residual stress generated during the high-temperature service of thermal barrier coatings is the key factor leading to their failure. The present research paper details the development, comprehensive characterisation, and mechanistic investigation of a novel series of Y3Al5O12:xCe³⁺ (YAG:xCe, x = 0.03, 0.06, 0.08, 0.12) fluorescent stress-responsive units, which have been engineered specifically for the non-destructive, in-situ stress monitoring of thermal barrier coatings (TBCs). The primary objective is to establish and optimize the critical linkage between the atomic-scale structure, governed by dopant concentration, and the macroscopic stress-sensing performance, thus surpassing conventional fluorescence intensity optimization. The YAG:xCe composite powders were synthesised via a solid-state reaction at 1 400 °C for 6 hours under a vacuum atmosphere, with high-purity Y3Al5O12 and CeO2 as precursors. The resulting phase-pure powders, confirmed by X-ray diffraction (XRD), were subsequently deposited as ceramic layers onto substrates using atmospheric plasma spraying (APS) with meticulously controlled parameters (current: 620 A, primary gas: Ar). A suite of advanced characterization techniques was employed: X-ray diffraction (XRD) with Rietveld refinement was utilized for the precise determination of lattice parameters. Photoluminescence (PL) spectroscopy was employed for excitation/emission analysis. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) was used for microstructural and elemental mapping. Density functional theory (DFT) calculations were conducted for electronic structure analysis. The experimental data revealed a definitive and nuanced structure-property relationship. XRD Rietveld refinement quantified a systematic linear increase in the cubic lattice parameter from approximately 12.010 1 Å (x=0.03) to 12.019 2 Å (x=0.12), providing direct evidence of lattice expansion due to the larger ionic radius of Ce3+ (1.14 Å) compared to Y3+ (1.019 Å). Photoluminescence studies demonstrated that the absolute fluorescence intensity peaked at a doping concentration of x=0.06, indicative of the onset of concentration quenching at higher levels. Crucially, and diverging from simple intensity-based optimization, the stress-sensing sensitivity—defined by the magnitude of fluorescence peak shift (piezospectroscopic coefficient) per unit applied stress—reached its maximum at a different, higher concentration of x=0.08. This pivotal finding of decoupled optimal concentrations for luminescence efficiency (x=0.06) and stress sensitivity (x=0.08) forms the central innovation of this work. It is explained by a competitive mechanism: while higher doping enhances lattice strain and crystal field tunability (beneficial for sensitivity), it also concurrently increases non-radiative energy transfer pathways (detrimental to overall brightness). The YAG:0.08Ce composition represents the optimal balance where the strain-induced enhancement of the crystal field's responsivity to external stress outweighs the detrimental effects of incipient quenching. DFT calculations corroborate this by showing a downshift in the Ce³+ energy levels with increased doping, which directly lowers the 4f-5d transition energy, manifesting as the observed red-shift in emission spectra. In conclusion, the present study successfully constructs a series of YAG:xCe fluorescent stress-responsive units and demonstrates that their luminescence efficiency and stress-responsive characteristics can be effectively tuned by the doping concentration. The structure-property relationship among doping concentration, lattice distortion, and the piezospectroscopic effect is elucidated. The present work provides a substantial material system and theoretical foundation for achieving highly sensitive, non-destructive, and in-situ monitoring of the internal stress state in TBCs, thus offering positive support for the health monitoring and lifetime prediction of next-generation aero-engine thermal barrier coatings.
关键词
热障涂层 /
荧光 /
应力 /
YAG:Ce
Key words
thermal barrier coatings /
fluorescence /
stress /
YAG:Ce
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基金
国家自然科学基金（52462010）; 甘肃省级科技计划基础研究计划项（25JRRA055,25JRRA077）; 兰州理工大学青年教师学科交叉研究培育项目; “111”计划（D21032）
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