Microwave dielectric properties of Li(Mg1−xNix)PO4 ceramics for LTCC applications

Li(Mg1−xNix)PO4 (x=0-0.1) ceramics were prepared by the conventional solid-state ceramic method. The formation of single-phase Li(Mg1−xNix)PO4 (x=0-0.1) solid solutions is confirmed by the X-ray diffraction (XRD) patterns. Ni2+ substitution for Mg2+ can lower the sintering temperature and improve the microwave dielectric properties of LiMgPO4 ceramics. The LiMg0.95Ni0.05PO4 ceramic sintered at 875 °C for 2 h can reach a maximum relative density of 97.1% and shows the microwave dielectric properties of εr=6.91, Q×f=98,600 GHz, and τf= −55.3 ppm/°C. The large negative τf value is adjusted to nearly zero with the addition of TiO2. The LiMg0.95Ni0.05PO4-TiO2 composite ceramic with 11 vol% TiO2 sintered at 875 °C for 2 h exhibits good microwave dielectric properties of εr=9.88, Q×f=50,800 GHz, and τf=-1.4 ppm/°C. The composite ceramic is chemically compatible with silver and promising for low-temperature cofired ceramic applications.