Coordinated modulation of thermal resistance and thermal expansion compatibility has become a chief concern in designing reliable environmental/thermal barrier coating candidates for Si-based ceramics. This study reports phonon behaviors and thermal properties of prototypical silicates X2-Y₂SiO₅ and γ-Y₂Si₂O₇. The nature of anharmonicity for low-frequency phonons is analyzed, and the finding is discussed with respect to specific crystal structures and interatomic force constants. Low lattice thermal conductivities (κ_L) basically derive from the giant phonon anharmonicity enhanced by interactions between low-frequency optic and acoustic phonons. γ-Y₂Si₂O₇ is predicted with considerably lower thermal expansion coefficient (α_V) than Y₂SiO₅. The mechanism is disclosed as an effect of the extensive number of low-frequency phonons with negative Grüneisen constants (contributing to negative thermal expansion) in γ-Y₂Si₂O₇, together with its higher elastic stiffness against internal thermal pressure at elevated temperature. A guideline for simultaneously approaching low κ_L and low α_V is proposed for searching promising E/TBC candidates.

在设计用于硅基陶瓷的可靠的环境/隔热涂层候选材料时，热阻和热膨胀相容性的协调调节已成为主要问题。这项研究报告声子的行为和原型硅酸盐的热性能X2-Y ₂的SiO ₅和γ-Y ₂的Si ₂ ö ₇。分析了低频声子非谐性的性质，并就特定的晶体结构和原子间力常数讨论了这一发现。低的晶格热导率（κ_大号）基本上从由低频光学和声学声子之间的相互作用增强的巨声子非谐派生。γ-Y ₂的Si ₂ ö ₇被预测与相当低的热膨胀系数（α _V比Y）₂的SiO ₅。该机制被公开为具有负Grüneisen常数低频声子的广泛数量的效果（促进负热膨胀）γ-Y ₂的Si ₂ ö ₇，以其对在升高的温度的内部热压力较高的弹性刚度一起。一种同时接近低方针κ_大号和低α _V提出了搜索看好E / TBC的候选人。