Temperature stable Li2Ti0.75(Mg1/3Nb2/3)0.25O3-based microwave dielectric ceramics with low sintering temperature and ultra-low dielectric loss for dielectric resonator antenna applications

Abstract

Microwave dielectric ceramics are considered to be one of the key materials of dielectric resonators/filters and have wide application prospects in fifth generation (5G) mobile communication systems. Here we prepared two kinds of low-sintering temperature and high-performance microwave dielectric ceramics with monoclinic rock salt structure by adding a small amount of V₂O₅ and 0.6CuO–0.4B₂O₃ sintering aids to Li₂Ti_0.75(Mg_1/3Nb_2/3)_0.25O₃ (LTMN_0.25). The sintering temperature of LTMN_0.25 ceramics with 2 wt% V₂O₅ and 1 wt% 0.6CuO–0.4B₂O₃ additions could be effectively reduced from 1170 °C to below 910 °C due to the liquid phase effects resulting from the additives. Typically, high performance microwave dielectric properties can be obtained in the LTMN_0.25 + 2 wt% V₂O₅ ceramic sintered at 910 °C for 2 h, with a ε_r ∼ 20.7, a Q × f ∼ 60 460 GHz and a TCF ∼ +4.3 ppm °C⁻¹. The best dielectric properties of ε_r ∼ 19.9, a Q × f ∼ 60 950 GHz and a TCF ∼ −6.1 ppm °C⁻¹ were obtained for the samples with 1 wt% 0.6CuO–0.4B₂O₃ sintered at 870 °C for 2 h. A prototype dielectric resonator antenna (DRA) was fabricated by LTMN_0.25 + 1 wt% 0.6CuO–0.4B₂O₃ ceramic. The antenna resonated at 10.02 GHz with a bandwidth ∼175 MHz at −10 dB transmission loss (S₁₁). Moreover, the chemical compatibility with Ag powder suggests that the LTMN_0.25 + 2 wt% V₂O₅ and LTMN_0.25 + 1 wt% 0.6CuO–0.4B₂O₃ ceramics may be suitable candidates for low temperature co-fired ceramic technology applications.