Two low-firing microwave dielectric ceramics Na₂LnMg₂V₃O₁₂ (Ln = Pr, Yb) and their chemical compatibility with silver

Two low-firing Na₂LnMg₂V₃O₁₂ (Ln = Pr, Yb) ceramics were prepared by the conventional solid-state reaction method, and the sintering behavior, phase purity, and microwave dielectric properties were investigated. Both ceramics crystallized in a cubic garnet structure and could be well densified below 900 °C. Na₂PrMg₂V₃O₁₂ sintered at 860 °C/4 h had ε _r  = 12.6, Q × f = 15,040 GHz, τ _f  = −45.1 ppm/°C, and Na₂YbMg₂V₃O₁₂ possessed the optimum microwave dielectric properties with ε _r  = 13.1, Q × f = 22,040 GHz, τ _f  = −59.2 ppm/°C when sintered at 820 °C/4 h. LiCa₂Mg₂V₃O₁₂ was chosen as a τ _f compensator to tailor the thermal stability of Na₂LnMg₂V₃O₁₂ due to the same structure and its large positive τ _f value. Temperature-stable ceramics based on (1−x) Na₂LnMg₂V₃O₁₂–xLiCa₂Mg₂V₃O₁₂ were obtained with near-zero τ _f values of +0.5 and −1.6 ppm/°C, respectively, when sintered at 820 °C/4 h. Both compounds did not react with the commonly used silver electrodes.