Novel Al 2 Mo 3 O 12 -based temperature-stable microwave dielectric ceramics for LTCC applications

Microwave dielectric ceramics are key materials in low-temperature co-fired ceramic (LTCC) technology. In many material systems, Mo-based microwave dielectric ceramics have attracted world-wide attention in recent years due to their low intrinsic sintering temperature and high quality factor ( Q × f ). In combination with its low dielectric constant ( ε r ), Al 2 Mo 3 O 12 is a very promising LTCC candidate, but the very negative temperature coefficient of its resonant frequency ( τ f ) limits its application. In this work, novel (1 − x )Al 2 Mo 3 O 12 – x TiO 2 ( x = 0–0.4) microwave dielectric ceramics were designed and prepared by a conventional solid-state reaction. The effects of TiO 2 addition on the phase composition, microstructure, and microwave dielectric properties of the obtained Al 2 Mo 3 O 12 -based ceramics were investigated. It was revealed that rutile TiO 2 could co-exist with monoclinic Al 2 Mo 3 O 12 in the samples after they were prepared under optimized conditions. With increasing addition of TiO 2 , the ε r value of the obtained ceramics increased from 5.69 to 6.85, the value of Q × f decreased from 73 910 to 45 720 GHz, and τ f varied from −32.3 to +9.2 ppm °C −1 . When x = 0.3, microwave dielectric ceramics of near-zero τ f ( ε r = 6.23, Q × f = 51 630 GHz, and τ f = −3.3 ppm °C −1 ) could be obtained. Such high-performance microwave dielectric ceramics would be promising for LTCC applications.