Water and SnF₂ Assisted Ultralow-Temperature Sintering of Mechanically Tough Y₃Fe₅O₁₂ Composites for Magneto-Dielectric Antennas

Abstract

Recently, the cold sintering process (CSP) has gained worldwide recognition from the scientific community as a green and innovative fabrication technique due to the substantial reduction of processing energy, time, and cost. The present work reports the preparation, fabrication, and properties of (1 – x )Y 3 Fe 5 O 12 – x SnF 2 ( x = 0.2, 0.3, 0.4, 0.5 volume fraction) ceramic composites for the first time through the cold sintering process under 150 °C, by applying 300 MPa uniaxial pressure for 30 min. The evolved microstructures of the cold-sintered composites suggest enhanced densification with increasing SnF 2 concentration. The evolution of the microstructure, consequent densification, and hardness of the composites can be due to the combined effect of water as a transient solvent and the relatively low melting point of SnF 2 . The main mechanism behind the densification in the SnF 2 -based system can be the liquid phase formation followed by pressure solution creep and plastic deformation. At the optimum additive concentration, the measured microhardness of the composite is around 4.7 GPa and its moisture absorption lies below 0.1%. The (1 – x )YIG– x SnF 2 ceramics have relative permittivity (ε r ) in the range of 7.1–11.3 and loss tangent of the order of 10 –2 at a frequency of 900 MHz. Further, the real part of permeability and the corresponding loss tangent lie below 2 and 10 –1, respectively, at 900 MHz. Herein, a microstrip patch antenna (MPA) is designed, simulated, and fabricated using the 0.5YIG–0.5SnF 2 composite, which shows excellent performance at 5.29 GHz with a return loss of −17.9 dB and an impedance bandwidth of 780 MHz. Hence, cold sintering using SnF 2 -based additives is considered a sustainable, energy-efficient, and cost-effective tool for the densification of magneto-dielectric materials.

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