(NaBi)_0.5MoO₄–BiPO₄ microwave dielectric ceramics with ultra-low sintering temperatures

A series of (1−x)(NaBi)_0.5MoO₄–xBiPO₄ microwave dielectric ceramics with ultra-low sintering temperatures (< 700 °C) are introduced in this work. The phase compositions, microwave dielectric properties and temperature dependences were studied. A small amount of BiPO₄ occupies the scheelite position forming a solid solution. Tetragonal scheelite phase together with low temperature phase (LTP) and high temperature phase (HTP) coexist in the (1−x)(NaBi)_0.5MoO₄–xBiPO₄ microwave dielectric ceramics. The scheelite phase and HTP dominate the composition sintered at relatively low temperatures of 600–650 °C. With x increasing from 0 to 0.6, the microwave permittivities, Q×f and τ_f values increase first and then decrease with ε_r = 37.6 – 26.8, Q×f = 17,500 – 5500 GHz, and τ_f = (− 3.3) – 109.5 ppm/ °C. When x = 0.5, the microwave dielectric ceramic sintered at 650 °C exhibits optimal temperature stability with τ_f = − 0.3 ppm/ °C, and the dielectric properties at low frequencies have a good temperature stability in a wide temperature range of − 170 and 200 °C. Meanwhile, the (NaBi)_0.5MoO₄–BiPO₄ ceramic shows a good chemical compatibility with aluminum (Al) electrode material, making it promising for the ULTCC application.