Journal of Advanced Materials in Engineering

Journal of Advanced Materials in Engineering

Investigating the Role of Substituted Cations (Mn4+ and Ni2+ Replacing Al3+) in the Microwave Dielectric Behavior of Cordierite Electroceramics

Articles in Press

Document Type : Original Article

Authors
Mohammadmehdi Rashidi
Mahdi Feizpour
Hadi Barzegar Bafrooei
Department of Materials Science and Engineering, School of Engineering, Meybod University, Yazd, Iran
Abstract
Introduction and Objectives: Cordierite ceramics (Mg2Al4Si5O18) are recognized as advanced dielectric materials due to their low dielectric constant, very low dielectric loss, high thermal stability, and optimal performance in microwave and millimeter-wave frequency ranges. These materials are utilized in fifth- and sixth-generation (5G and 6G) communication systems. This study investigates the simultaneous substitution effects of Mn⁴⁺ and Ni²⁺ cations for Al³⁺ on the densification, crystalline structure, microstructure, mixing entropy (ΔSmixing), and dielectric properties of cordierite ceramics.
Materials and Methods: Samples with different substitution levels (0, 0.25, and 0.50) were prepared by the solid-state synthesis method and subsequently sintered at various temperatures. Phase and microstructural analyses were carried out using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. A network analyzer was employed to measure the dielectric properties at microwave frequencies. In addition, the mixing entropy and lattice distortion were measured, analyzed, and discussed.
Results: It was observed that substituting Mn4+ and Ni2+ for Al3+ results in achieving the maximum density at a temperature about 100 °C lower than that of pure cordierite. X-ray diffraction and Raman spectroscopy analyses indicated that a complete solid solution is formed at x=0.25, whereas increasing x to 0.50 results in the appearance of a secondary phase, Mg1.16Mn0.84Si2O6, in addition to the cordierite phase. Microstructural observations also revealed that the average grain size increases with higher substitution levels. The optimal microwave dielectric properties were obtained for Mg2Al3.75(Mn4+Ni4+)0.25Si5O18, with εᵣ= 4.58, Q×f =107333 GHz, and τf = –14.7 ppm/°C, while the value of ΔSmixing was measured to be 2.30 J/mol · K.
Conclusion: Controlled substitution of Mn4+ and Ni2+ at an appropriate sintering temperature enables simultaneous optimization of dielectric properties and thermal stability.
Keywords
Cordierite
Microwave dielectric properties
Electroceramics
Entropy of mixing
Lattice distortion
Fifth and Sixth generations of communications (5G
6G)
Subjects
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