Microwave dielectric properties of temperature-stable (Na0.5Bi0.5)MoO4–SrMoO4 ceramics sintered at ultra-low temperature

Abstract

Ever-growing wireless communication industry demands low loss dielectric ceramics with exceptional microwave dielectric properties and ultra-low sintering temperatures. In this work, a solid solution (1 − x)Na_0.5Bi_0.5MoO₄–xSrMoO₄ referred as (1 − x)NBM–xSM (x = 0.4–0.9) was prepared through replacing (NaBi)²⁺ by Sr²⁺. X-ray diffraction analysis (XRD) revealed a solid solution ceramics characterized by a tetragonal scheelite structure. Scanning electron microscopy (SEM) and relative density further confirmed the formation of low porosity and high density scheelite solid solution ceramics. Optimum microwave dielectric performance with a relative permittivity of 15.48, $Q\times f$ value of 18 763 GHz and a near-zero temperature coefficient of resonant frequency (${\tau }_f$ = +2.7 ppm/°C) was achieved at x = 0.7 composition with ultra-low sintering temperature of 660°C. In order to validate its microwave device application, a prototype dielectric resonator antenna (DRA) was fabricated using the 0.3NBM–0.7SM ceramic. DRA showcased excellent radiation performance, with impedance bandwidth of 200 MHz at a working frequency of 6.83 GHz and realized gain of 5.66 dBi. The co-firing investigations demonstrate Ag powder exhibits excellent chemical compatibility with the (1 − x)NBM–xSM ceramics, confirming a promising potential of the (1 − x)NBM–xSM (x = 0.4–0.9) solid solution ceramics for ultra-low temperature co-fired ceramics-based microwave application.