The structure and microwave dielectric properties of Li₂MoO₄-SiO₂ ceramics without addition of glass as sintering aids

Abstract

SiO2 ceramic is one of the most important candidate materials for high-frequency microwave ceramics with very low dielectric constant (εr) at around 3.8 and low dielectric loss. However, a high sintering temperature must be provided during the preparation, which restricted their further application in low temperature co-fired ceramic (LTCC) field. In the present work, Li2MoO4-(1+δ)SiO2 (δ =-0.5,-0.2, 0, 0.2, 0.5 mole) ceramics were prepared by solid-state reaction method and sintered at 800 °C. XRD, SEM, EDS and Raman spectroscopy techniques were used to study the phase composition and crystal structure. The ceramic samples were composed of both Li2MoO4 and SiO2 phases. The εr values decrease with increased δ, which agree with the Lichtenecker logarithmic rule. The quality factor (Q×f) value initially increased and then decreased with increased δ. When evaluated as a microwave dielectric material, the Li2MoO4-(1+δ)SiO2 ceramics show excellent dielectric performance with a low dielectric constant (εr = 4.807) and high Q×f values of ~21000 GHz at δ = 0 as sintered at 800 °C, which is a possible candidate for LTCC.