Thermal Properties and Thermal Shock Resistance of γ‐Y ₂ Si ₂ O ₇

Abstract

Thermal properties, namely, Debye temperature, thermal expansion coefficient, heat capacity, and thermal conductivity of γ‐Y 2 Si 2 O 7 , a high‐temperature polymorph of yttrium disilicate, were investigated. The anisotropic thermal expansions of γ‐Y 2 Si 2 O 7 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‐Y 2 Si 2 O 7 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‐Y 2 Si 2 O 7 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, κ min , was 1.35 W·(m·K) −1 . The unique combination of low thermal expansion coefficient and low‐thermal conductivity of γ‐Y 2 Si 2 O 7 renders it a very competitive candidate material for high temperature structural components and environmental/thermal‐barrier coatings. The thermal shock resistance of γ‐Y 2 Si 2 O 7 was estimated by quenching dense materials in water from various temperatures and the critical temperature difference, Δ T c , was determined to be 300 K.