Microwave dielectric properties of (Na _0.5 Bi _0.5 )MoO ₄ –BaMoO ₄ composite ceramics with ultralow sintering temperature

Abstract

Abstract The rapidly ever‐growing wireless communication demands development of low loss, ultralow sintering temperature dielectric ceramics with excellent microwave properties. In this work, fabrication and properties of novel microwave dielectric composite ceramics (1 − x )(Na 0.5 Bi 0.5 )MoO 4 – x BaMoO 4 ( x = 0.3–0.6), in short as ((1 − x )NBM– x BM), synthesized via solid‐state reaction method with an ultralow sintering temperature is reported. X‐ray diffraction analysis confirms the coexistence of both (Na 0.5 Bi 0.5 )MoO 4 and BaMoO 4 scheelite phases. Scanning electron microscopy analysis demonstrated dense microstructures of ceramics sintered at 650°C and 700°C. The dielectric properties of (1 − x )NBM– x BM ( x = 0.3–0.6) ceramic are significantly tailored by incorporation of BaMoO 4 . With the increase in x from 0.3 to 0.6, the (1 − x )(Na 0.5 Bi 0.5 )MoO 4 – x BaMoO 4 displays noticeable change in microwave permittivity (varying from 25.4 to 16.6), quality factor values, and temperature coefficient of frequency (range tunable from +37.6 ppm/°C to −14.2 ppm/°C). The microwave dielectric ceramic, 0.5(Na 0.5 Bi 0.5 )MoO 4 –0.5BaMoO 4 , has optimum dielectric properties (, = 15 164 GHz, τ f = −0.2 ppm/°C) at sintering temperature of 650°C. The dielectric resonator antenna designed using (1 − x )(Na 0.5 Bi 0.5 )MoO 4 – x BaMoO 4 ceramics demonstrated excellent radiation performance at resonance frequency of 5.905 GHz, gain of ∼5.8 dBi and 140 MHz bandwidth, which validates its microwave applications utilization within the field of ultralow temperature cofired ceramics technology.