Structure, thermal and microwave dielectric properties of cold-sintered Li2MoO4Al2O3 ceramic

Abstract

Dielectric ceramics are essential components in communication systems that operate within the microwave frequency range. In high-density packages, dielectric substrates ceramics must possess high thermal conductivity to efficiently dissipate heat. However, achieving adequate thermal conductivity (κ) in ceramics sintered at low temperatures is challenging. In this study, we employed the cold sintering process (CSP) to fabricate Li₂MoO₄-x%Al₂O₃ (0≤x ≤ 80, in volume) ceramics under 200 MPa pressure at 150 °C. The Li₂MoO₄40%Al₂O₃ composite exhibited significantly enhanced κ of 5.4 W·m⁻¹·K⁻¹, an 80% increase compared to pure Li₂MoO₄ ceramic with κ of 3 W·m⁻¹·K⁻¹. At 40% Al₂O₃ content, the Li₂MoO₄Al₂O₃ ceramic demonstrated notable microwave properties (ε ∼ 6.67, Q×f ∼ 17,846 GHz, τ_f ∼ −105 × 10⁻⁶ °C^-1). Additionally, simulation of a microstrip patch antenna for 5 GHz applications using Li₂MoO₄20%Al₂O₃ ceramic as dielectric substrate via Finite Element Simulation software showed excellent performance, with radiation efficiency exceeding 99% and low return loss (S₁₁ < −30 dB) at both 4.9 GHz and 28.0 GHz center frequencies. These findings underscore the suitability of Li₂MoO₄Al₂O₃ ceramics for microwave dielectric substrate.