A low-firing Ca5Ni4(VO4)6 ceramic with tunable microwave dielectric properties and chemical compatibility with Ag

A Ca5Ni4(VO4)6 low loss microwave dielectric ceramic with A site deficient garnet structure was prepared via the conventional solid state reaction method. Ca5Ni4(VO4)6 sintered at 980 °C for 4 h to a relative density of 96.2% exhibits favorable microwave dielectric properties such as a permittivity of 10.9, a Q×f value of 96,500 GHz, and a τf value of −63.6 ppm/°C. Its large negative τf could be compensated by forming a solid solution with LiCa2Mg2V3O12, that led to improved properties with a near-zero τf=−3.7 ppm/°C, εr=10.2, Q×f=59,300 GHz for 0.8Ca5Ni4(VO4)6−0.2LiCa2Mg2V3O12 after sintering at 955 °C for 4 h. Further on, 0.8Ca5Ni4(VO4)6−0.2LiCa2Mg2V3O12 proved to be chemically compatible with Ag electrodes, so it might be a possible candidate for LTCC applications.