Effect of Si ⁴⁺ substitution on mechanical and thermal expansion properties of Ca _0.5 Sr _0.5 Zr ₄ P ₆ O ₂₄ ceramics

Abstract The Ca _{(1+ x )/2} Sr _{(1+ x )/2} Zr ₄ P _{6‐2 x} Si _{2 x} O ₂₄ (CSZP _{6‐2 x} S _{2 x} , 0 ≤ x ≤ 0.3) ceramics were prepared using powders synthesized by co‐precipitation method, and the effects of Si ⁴⁺ substitution on the structure, mechanical, and thermal expansion properties were investigated. The optimum sintering time was 4 hours, which greatly shortened the sintering process. By controlling the appropriate composition and sintering temperature, a single phase with the typical NaZr ₂ P ₃ O ₁₂ structure was obtained. As a function of x increasing, the parameter a increased and then decreased, while the parameter c and unit cell volume both increased. The mechanical property of CSZP _{6‐2 x} S _{2 x} ceramics was affected with increasing amount of Si ⁴⁺ content. The Si ⁴⁺ substitution could increase the thermal expansion anisotropy and lead to the generation of microcracks, which are responsible for the increase in the amount of hysteresis between heating and cooling curves. The thermal expansion decreased progressively from 1.8 to 0.8 × 10 ⁻⁶ /°C. The investigations indicate that the CSZP _{6‐2 x} S _{2 x} ceramics are potential materials in high temperature applications