Ultralow-loss (1-x)CaWO₄-xNa₂WO₄ (x = 0.1, 0.2) microwave dielectric ceramic for LTCC applications

In this work, the (1-x)CaWO₄-xNa₂WO₄ (x = 0.1, 0.2, denoted as 0.9CW-0.1NW and 0.8CW-0.2NW, respectively) ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method. Using low melting-point Na₂WO₄ as sintering aid to prepare CaWO₄Na₂WO₄ composite ceramics, the sintering temperature of CaWO₄ was successfully reduced while maintaining excellent microwave performance. The optimal microwave dielectric properties have been achieved at 900 °C for 0.9CW-0.1NW ceramic: ε_r = 9.0, Q × f = 105660 GHz, tanδ = 1.1 × 10⁻⁴ and τ_f = −35.4 ppm/°C at a frequency of 12.0 GHz. For the 0.8CW-0.2NW ceramic, the optimal microwave dielectric properties have been obtained at 740 °C, with ε_r = 8.5, Q × f = 97014 GHz, tanδ = 1.2 × 10⁻⁴ and τ_f = −37.4 ppm/°C at a frequency of 11.8 GHz. In summary, both composite ceramics exhibit low sintering temperatures, excellent dielectric properties and chemical compatibility with the Ag electrode. The findings of this study provide an effective approach to prepare novel composite ceramics as promising candidates for LTCC applications.