Microwave dielectric ceramics Li₂MO₄-TiO₂ (M = Mo, W) with low sintering temperatures

In this work, novel series of (1 - x)Li₂MO₄-xTiO ₂ (M = Mo, W; x = 0.3, 0.4, 0.45, 0.5, 0.6) ceramics were developed for microwave dielectric application. They were prepared via the mixed-oxide process and the phase composition, microstructures, sintering behaviors, and microwave dielectric properties were investigated. The X-ray diffraction (XRD) pattern and scanning electron microscope analysis indicated that the Li ₂MO₄ (M = Mo, W) did not react with rutile TiO₂ and a stable two-phase composite system Li₂MO₄-TiO ₂ (M = Mo, W) was formed. The XRD pattern of cofired ceramics revealed that some parts of Li₂MoO₄ phase and very small part of Li₂WO₄ phase react with Ag to form Ag ₂MoO₄ phase and Ag₂WO₄ phase, respectively. At x = 0.45-0.5, temperature stable microwave dielectric materials with low sintering temperature (700°C-730°C) were obtained: ε_r = 10.6-11.0, Qf = 30 060-32 800 GHz, and temperature coefficient of resonant frequency ∼0 ppm/°C.