Garnet mineral based composites through cold sintering process: Microstructure and dielectric properties

摘要

In the present study, a mineral garnet (Fe1.72Mg0.8Mn0.01Ca0.02)(2+) (Fe0.04Al2.36)(3+) Si2.934+O12 which decomposes above 600 degrees C was densified using cold sintering process. Composites of the garnet with different weight percentages of NaCl and Li2MoO4 were fabricated using water as a solvent. These composites heat treated at 120-250 degrees C under a uniaxial pressure of 450 MPa for 50 min showed 80-95 % of theoretical densities. The influences of amount of additives, cold sintering time and temperature on the microstructure and dielectric properties of the composites were investigated. As the amount of NaCl and Li2MoO4 increases, the grain boundaries become more evident and the garnet grains are segregated between the grains of additives due to the capillary force and pressure gradient. Garnet-NaCl and garnet-Li2MoO4 composites possess relative permittivity of 6-8 and quality factor (Q(u)x f) > 2000 GHz (f approximate to 10 GHz) at microwave frequencies.