NaCa₄V₅O₁₇: A low-firing microwave dielectric ceramic with low permittivity and chemical compatibility with silver for LTCC applications

Phase formation, crystal structure and dielectric properties of NaCa₄V₅O₁₇ ceramics fabricated via a solid state reaction route at relatively low temperatures (780-860 °C) were investigated. NaCa₄V₅O₁₇ crystallizes in a triclinic structure. Dielectric properties were measured based on the Hakki-Coleman post resonator method at microwave frequency. Specially, a specimen sintered at 840 °C demonstrated balanced dielectric properties with a permittivity ε_r = 9.72, a quality factor Q×f = 51,000 GHz, and a temperature coefficient of resonance frequency τ_f = -84 ppm/°C. NaCa₄V₅O₁₇ ceramics showed excellent chemical compatibility with Ag metal electrodes. Besides, the thermal stability of resonance frequency was effectively adjusted through formation of composite ceramics between NaCa₄V₅O₁₇ and TiO₂ and a near-zero τ_f ∼ 1.3 ppm/°C accompanied with ε_r = 14.9 and Q×f = 19,600 GHz was achieved when 50% mol TiO₂ was added. All the merits render NaCa₄V₅O₁₇ a potential candidate for multilayer electronic devices.