The spectra analysis and microwave dielectric properties of [Ca _0.55 (Sm _1-x Bi _x ) _0.3 ]MoO ₄ ceramics

A series of low-temperature firing ceramics with scheelite structure, [Ca _0.55 (Sm _1-x Bi _x ) _0.3 ]MoO ₄ (x = 0.2–0.95), were prepared via solid-state reaction. The sintering temperature ranges from 660 to 760°C. A standard tetragonal scheelite phase was formed without secondary phase. When the x value was 0.95, the temperature coefficient of resonant frequency (τ _f ) moved to a near zero value (−2.1 ppm/°C) with a dielectric constant 13.7 and the quality factor (Qf) of 33 200 GHz. The Raman spectra shows that the more vibration modes appeared with x value, which is due to the increasing of Bi concentration and results in increase in permittivities and decrease in Qf values. The classical harmonic oscillator model is used in the infrared spectra and extrapolate to the microwave range. The [Ca _0.55 (Sm _1-x Bi _x ) _0.3 ]MoO ₄ ceramics show high-performance microwave dielectric properties at low-sintering temperature.