(1 − x)CaTiO3–x(Li0.5Nd0.5)TiO3 for ultra-small dielectrically loaded antennas

Microwave (MW) dielectric ceramics based on the solid solution (1 − x)CaTiO3–x(Li0.5Nd0.5)TiO3 (0.25 ≤ x ≤ 1.0) were prepared by conventional solid-state synthesis using the mixed oxide route. Compositions closest to zero τf (+65 ppm/°C) were obtained at x = 0.8 where er = 110 and the microwave quality factor, Qf0 ≅ 2600 GHz for samples sintered at 1300 °C. To reduce the sintering temperature and compensate for any Li2O loss during fabrication, ≤0.5 wt% 0.5Li2O–0.5B2O3 was added as a sintering aid in the form of raw oxides (LBR) and also as a pre-reacted glass (LBG). 0.5 wt% LBR was the most effective, reducing the temperature to achieve optimum density by ~50 °C with no significant deterioration of microwave properties (er = 115, τf = +65 ppm/°C and Qf0 ≅ 2500 GHz). The high permittivity and relatively low sintering temperatures (1250 °C) are ideal for the development of low cost ultra-small dielectric loaded antenna, assuming the system can be tuned closer to zero by fractionally increasing x.