High quality factor cold sintered Li2MoO4BaFe12O19 composites for microwave applications

Abstract

Abstract Ceramics-ceramic composites in series (1-x)Li2MoO4-xBaFe12O19 (LMO-BF12, 0.00\u202f≤\u202fx\u202f≤\u202f0.15) have been cold sintered at 120\u202f°C and their structure and properties characterized. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that compositions were dual phase and had a dense microstructure. Composites in the xBF12-(1-x)LMO (0.0\u202f≤\u202fx\u202f≤\u202f0.15) series resonated at MW frequencies (∼6\u202fGHz) with 5.6≤er\u202f≤\u202f5.8 and Qf\u202f=\u202f16,000–22,000\u202fGHz, despite the black colour of compositions with x\u202f>\u202f0. The permeability of the composites was measured in the X band (∼8\u202fGHz) and showed an increase from 0.94 (x\u202f=\u202f0.05) to 1.02 (x\u202f=\u202f0.15). Finite element modelling revealed that the volume fraction of BF12 dictates the conductivity of the material, with a percolation threshold at 10\u202fvol% BF12 but changes in er as a function of x were readily explained using a series mixing model. In summary, these composites are considered suitable for the fabrication of dual mode or enhanced bandwidth microstrip patch antennas.