3D printing and pressureless sintering of Li₂TiO₃ for next generation dielectric resonator antennas

Direct-write additively manufactured (AM) high-performance lithium titanate (Li₂TiO₃) 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 Li₂CO₃ and LiCl that formed due to reactions between the dispersing phase and Li₂TiO₃ and other contaminants could not be completely removed which likely limited the achievable density and dielectric loss. Dielectric resonator antennas fabricated from the printed Li₂TiO₃ 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.