Preparation, Thermophysical and Mechanical Properties, Sintering Behavior of HfSiO ₄ Ceramic

ABSTRACT

HfSiO ₄ ceramic was successfully fabricated at 1650°C. Its thermal conductivity, coefficient of thermal expansion (CTE), mechanical properties, and high‐temperature sintering behavior were investigated. The results show that when the ratio of HfO ₂ to SiO ₂ in the raw materials is 1:1.04 (molar ratio), the prepared ceramic bulk materials are mainly composed of 99.30 mol% HfSiO ₄ and 0.7 mol% HfO ₂ phases. The thermal conductivity of HfSiO ₄ decreases with the increase of temperature, dropping to 2.15 W m ⁻¹  K ⁻¹ at 1200°C. The average CTE is 4.72 × 10 ⁻⁶ K ⁻¹ from room temperature to 1400°C, which is close to that of SiC. The phase composition of HfSiO ₄ ceramics remained unchanged after sintering at 1500°C for 150 h, demonstrating excellent high‐temperature phase stability. The fracture toughness and elastic modulus first increased and then tended to stabilize, reaching (3.154 ± 0.031) MPa m ^1/2 and (265.94 ± 13.55) GPa after sintering. The above research results indicate that HfSiO ₄ is one of the potential candidate materials to replace traditional Si bond material in ultra‐high temperature environmental barrier coating systems.