3D printing and pressureless sintering of LiTiO for next generation dielectric resonator antennas.

Direct-write additively manufactured (AM) high-performance lithium titanate (LiTiO) microwave RF ceramic with comparable density, dielectric constant, dielectric loss, and quality factor to traditionally made equivalents is demonstrated. Increasing the surface-to-volume ratio and interfacial free energy in designed electrosteric slurries is shown to be effective for driving pressureless sintering and porosity elimination. A relative density as high as 96.4% was achieved without the application of pressure. [Formula: see text] values up to 45,000 GHz, dielectric constants ([Formula: see text]) up to 19, and loss tangents ([Formula: see text]) of 1E-3 were achieved at ~ 14 GHz and correlated well with densification. However, compounds such as LiCO and LiCl that formed due to reactions between the dispersing phase and LiTiO and other contaminants could not be completely removed which likely limited the achievable density and dielectric loss. Dielectric resonator antennas fabricated from the printed LiTiO using a convergent manufacturing approach exhibited a bandwidth of 16‒18 GHz and gain peaking at 8.42 dBi between 16.25‒18.0 GHz. Over this range, the measured total efficiency remained above 90%, highlighting the low-loss nature of the resonator material and structure. The results show the potential of direct-write AM and convergent manufacturing approaches for the development and customization of printed, next-generation, ceramic RF materials and passives.