Synthesis, microstructure, hardness, thermal expansion, and dielectric properties of cordierite

Abstract A cordierite precursor powder was synthesized using the sol–gel method and then sintered to produce a dense cordierite with a minimal amount of Mg–Al spinel and cristobalite. Thermal and spectroscopic techniques were employed to analyze both the synthesized powder and the bulk material. The results indicated that μ‐cordierite began forming at 900°C and disappeared at 1300°C, while α‐cordierite began forming at 1200°C, and its fraction increased to 98.44% at 1400°C. Cordierite formation energies obtained from differential thermal analysis (DTA) results ranged from 653.41 to 685 kJ mol −1 . Bulk crystallization, controlled by three‐dimensional growth, was the dominant crystallization mechanism. The dense cordierite ceramic, sintered at 1450°C for 2 h, had a dielectric constant of 5.21 and a low loss tangent of 3.53 × 10 −3 at high frequencies. Additionally, it demonstrated a low coefficient of thermal expansion (CTE) of 1.89 × 10 −6 K −1 and a high hardness of 9.53 GPa, offering both thermal stability and strength. These material properties are attractive for a wide range of functional applications.