Microwave dielectric properties of low firing (Na_0.5Ln_0.5)MoO₄ (Ln=Nd and Ce) ceramics

A new series of sheelite structured (Na_0.5Ln_0.5)MoO₄ (Ln=Nd and Ce) ceramics was prepared by using the traditional solid state reaction method. The (Na_0.5Nd_0.5)MoO₄ ceramic could be well densified at 760 °C with excellent microwave dielectric properties (a permittivity of ∼10.5, a quality factor Q×f of ∼19,605 GHz (f=9.15 GHz) and a temperature coefficient of frequency of (TCF or τ_f)∼ -49 ppm/^oC). Meanwhile, the (Na_0.5Ce_0.5)MoO₄ ceramic sintered at 780 °C possessed the best microwave dielectric properties with a permittivity of ∼11.2, a Q×f value of 19,365 GHz (f=8.98 GHz) and TCF of approximately -44 ppm/ °C. The (Na_0.5Nd_0.5)MoO₄ ceramic was found to be chemically compatible with Ag electrode at its sintering temperature. It is a promising microwave dielectric material for low-temperature co-fired ceramic technology (LTCC). However, the (Na_0.5Ce_0.5)MoO₄ ceramic was found to react with Ag after co-firing at 780 °C for 2 h and this limited its application in LTCC technology.