Structural, microstructural, and microwave dielectric properties of (Al1-B )2Mo3O12 ceramics with low dielectric constant and low dielectric loss for LTCC applications

The (Al1-xBx)2Mo3O12 ceramics with double phases were prepared by solid-phase sintering method at the temperature from 725 to 800 °C for LTCC application. Through XRD pattern and Rietveld refinement analysis, it was confirmed that the (Al1-xBx)2Mo3O12 composition consists of the coexistence of double phase (the monoclinic structure of the P21/a space group and the orthorhombic structure of the Pnca space group), and the orthorhombic phase was increased with boron substitution. The microwave dielectric properties of the (Al1-xBx)2Mo3O12 ceramic series were impacted by double-phase formation (crystal structure ratio), which increases the densification and grain uniformity. With the boron substitution, the (Al1-xBx)2Mo3O12 ceramic series demonstrate outstanding microwave dielectric properties (εr = 4.04, Q × f = 35870 GHz @ 15 GHz, τƒ = 4.2 ppm/°C) with high relative density (ρrel ≈ 98.84%) and thermal conductivity κ = 0.88 W/m.K for x = 0.3 at 775 °C, indicate that it is a promising candidate for LTCC substrate material.