Cold Sintering: An Energy-Efficient Process for the Development of SrFe<sub>12</sub>O<sub>19</sub>–Li<sub>2</sub>MoO<sub>4</sub> Composite-Based Wide-Bandwidth Ferrite Resonator Antenna for Ku-Band Applications
Athira Rajan, Sibi Kaithakkal Solaman, Subodh Ganesanpotti
Abstract
A sustainable cold-sintering process was adopted to fabricate composites of (1–x)SrFe12O19–xLi2MoO4, x = 0.4, 0.5, 0.6, and 0.7 with density up to 91%, and their broad-band electromagnetic properties were deciphered. X-ray diffraction (XRD) analysis revealed the coexistence of SrFe12O19 (SFO) and Li2MoO4 (LMO) phases in the composites, unaccompanied by any additional phases. The evolution of microstructure facilitating enhanced densification was observed with an increase in the LMO volume fraction. The real permittivity (ε′) increased with an increase in the LMO volume fraction, while the dielectric loss (tan δε) decreased. Further, the real permeability (μ′) of all of the composites is greater than unity and the magnetic loss (tan δμ) is of the order of 10–2. The 0.3SFO–0.7LMO composite with the highest densification possess ε′ = 6.7, tan δε = 2 × 10–3, μ′ = 1.14, and tan δμ = 2 × 10–2 at 900 MHz along with an appreciable room-temperature saturation magnetization (Ms) of 32.2 emu/g. To demonstrate the application potential of this magnetodielectric composite toward microwave antenna applications, a ferrite resonator antenna (FRA) integrated using the SFO–LMO composite was designed, simulated, and fabricated. The fabricated FRA resonating at 12.89 GHz exhibited an exceptionally high return loss of −40 dB and a wide impedance bandwidth of 510 MHz. The remarkable properties of the fabricated ferrite resonator antenna suggest that it is a potential candidate for Ku-band applications.