L2Ti0.85(Mg1/3Nb2/3)0.15O3/MgTiO3/L2Ti0.85 (Mg1/3Nb2/3)0.15O3 tri-layer co-fired microwave dielectric ceramics: A strategy to suppress non-linear variation of resonant frequency with temperature and achieve a high Q value

In many microwave dielectric ceramics systems, like MgTiO3–CaTiO3, MgTiO3–SrTiO3, and tri-layer MgTiO3/TiO2/MgTiO3, the resonant frequency shows a non-linear variation over a wide temperature range (−40 – 105 °C), indicating that the negative τf (−40 – 25 °C) value deviates from zero when the positive τf (25–105 °C) value is tuned to zero. To suppress the non-linear variation of resonant frequency in the range of −40 – 105 °C, a well-established and efficacious method has been proposed by introducing Li2Ti0.85(Mg1/3Nb2/3)0.15O3 ceramic to the MgTiO3 system. Furthermore, a tri-layer architecture ceramic was designed to improve the dielectric properties. Compared with randomly distributed samples, the Q × f value can be increased by up to 51%. Moreover, the electric field distribution was simulated by the finite element method with the aid of the eigenmode solver of high frequency structure simulator (HFSS) to clarify the dielectric mechanism and predict the microwave dielectric characteristics of the tri-layer structure ceramics. Finally, tri-layer Li2Ti0.85(Mg1/3Nb2/3)0.15O3/MgTiO3/Li2Ti0.85(Mg1/3Nb2/3)0.15O3 ceramic with wide temperature stability and high Q × f value was obtained [εr = 18.4, Q × f = 85 000 GHz, τf+ = −3.8 ppm/°C (25–105 °C), τf− = 4.0 ppm/°C (−40 – 25 °C)], which refines the theory of non-linear variation of resonant frequency and holds promise for application in the 5G communication system.