Crystal structure, microwave dielectric properties, and dielectric resonant antenna studies of novel low-permittivity CoAlO spinel ceramics.

CoAlO spinel ceramics were prepared via a standard solid-state reaction method, and their crystal structure, microwave dielectric properties, and dielectric resonant antenna applications were systematically investigated in this study. X-Ray diffraction patterns and Raman spectra confirmed that CoAlO belongs to the -3 space group with cubic crystal symmetry. and values increased with the increasing sintering temperature, where an ever-improving microstructure was also observed from the scanning electron micrographs. The optimal microwave dielectric properties were achieved as follows:  = 9.34,  = 30,500 GHz, and  = -54 ppm/C. Moreover, a dielectric resonant antenna was designed and simulated to demonstrate the application prospects of CoAlO ceramics towards microwave antennas. The CoAlO-based antenna resonating at 14.33 GHz exhibited a high return loss of -40.9 dB, a wide impedance bandwidth of 940 MHz, and an exceptionally high total efficiency of 96.6%. The remarkable antenna performances suggested that CoAlO ceramics were promising candidates for wireless communication devices operating at the -band, provided can be further tuned toward zero.