Thermal Properties and Thermal Shock Resistance of γ‐Y2Si2O7

Abstract

Thermal properties, namely, Debye temperature, thermal expansion coefficient, heat capacity, and thermal conductivity of γ‐Y2Si2O7, a high‐temperature polymorph of yttrium disilicate, were investigated. The anisotropic thermal expansions of γ‐Y2Si2O7 powders were examined using high‐temperature X‐ray diffractometer from 300 to 1373 K and the volumetric thermal expansion coefficient is (6.68±0.35) × 10−6 K−1. The linear thermal expansion coefficient of polycrystalline γ‐Y2Si2O7 determined by push‐rod dilatometer is (3.90±0.4) × 10−6 K−1, being very close to that of silicon nitride and silicon carbide. Besides, γ‐Y2Si2O7 displays a low‐thermal conductivity, with a κ value measured below 3.0 W·(m·K)−1 at the temperatures above 600 K. The calculated minimum thermal conductivity, κmin, was 1.35 W·(m·K)−1. The unique combination of low thermal expansion coefficient and low‐thermal conductivity of γ‐Y2Si2O7 renders it a very competitive candidate material for high temperature structural components and environmental/thermal‐barrier coatings. The thermal shock resistance of γ‐Y2Si2O7 was estimated by quenching dense materials in water from various temperatures and the critical temperature difference, ΔTc, was determined to be 300 K.