Water-Assisted Densification and Broadband Dielectric Response of Cold-Sintered Gd3Fe5O12-SnF2 Composites

Technological breakthroughs in this era of 5G and IoT entail the sustainable fabrication of integrable and multifunctional compact devices using low-loss microwave dielectric materials. Nowadays, the miniaturization of devices using magnetodielectric materials fabricated through a green and sustainable cold sintering process has expanded the scope of applications in various fields of modern communication. Cold sintering, a novel ultra-low-energy sintering technique based on pressure solution creep mechanisms, is a potential strategy with impressive savings in energy, time, and cost. This present work highlights the dielectric response and microstructure of (1-x) Gd3Fe5O12-x SnF2 (x = 0.2, 0.3, 0.4, 0.5 volume fraction) ceramic composites fabricated via a water-assisted cold-sintering process at a temperature of 150 degrees C under 300 MPa pressure for 30 min. The novelty of using SnF2 with Gd3Fe5O12 in a cold sintering process lies in its ability to enhance densification, lower hygroscopicity, moderate relative permittivity (18.6 at 900 MHz), low loss (similar to 10(-2)), and its low melting temperature of 216 degrees C. This innovative approach improves the properties of ceramic composites at significantly low temperatures, showing the potential for sustainable and efficient fabrication. Microstructural studies of these composites indicate that, as the volume fraction of SnF2 increases, the densification of the composites rises to 94.6% due to consecutive mechanisms of particle rearrangement, compaction, dissolution, and diffusion of SnF2 through the liquid phase at the initial stage, followed by the evaporation of the liquid phase, resulting in the precipitation of the supersaturated phase at pores and interfaces, and, finally, the melting of SnF2 forms a glassy phase around the grain boundaries. After cold sintering, the relative density of (1-x) Gd3Fe5O12-x SnF2 composites ranges from 82.4% to 94.6% as x changes from 0.2 to 0.5. The relative permittivity (epsilon(r)) of these (1-x) Gd3Fe5O12-x SnF2 ceramic composites ranges from 10.1 to 12.6 with a dielectric loss (tan delta) of the order of 10(-2) at 900 MHz. Hence, water and SnF2-assisted cold sintering is an efficient fabrication route for compact and densified magneto-dielectric ceramic GdIG-SnF2 composites with electromagnetic parameter suitable for microwave applications like miniaturized antennae.