Preparation and microwave dielectric properties of Li(Mg1–xCox)PO4 ceramics for low-temperature cofired ceramic applications

Abstract Li(Mg 1– x Co x )PO 4 ( x =0–0.09) ceramics were prepared by the conventional solid-state ceramic method. The formation of single-phase Li(Mg 1– x Co x )PO 4 solid solutions is confirmed by the X-ray diffraction (XRD) patterns. Co 2+ substitution for Mg 2+ can lower the sintering temperature and enhance the Qf value of LiMgPO 4 ceramics. The LiMg 0.95 Co 0.05 PO 4 ceramic sintered at 875 °C reaches a maximum relative density of 97.4% and shows the microwave dielectric properties of e r =6.97, Qf =111,200 GHz, and τ f =–53.8 ppm/°C. The negative τ f value can be tuned nearly to zero by adding TiO 2 . The LiMg 0.95 Co 0.05 PO 4 –TiO 2 composite ceramic with 16.1 wt% TiO 2 sintered at 875 °C for 2 h shows a near-zero τ f value of +0.8 ppm/°C, together with an e r value of 9.97 and a Qf value of 58,200 GHz. The composite ceramic does not react with the commonly used electrode material silver and is a promising candidate for low-temperature cofired ceramic applications.