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

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.