Microwave dielectric properties of temperature-stable zircon-type (Bi, Ce)VO₄ solid solution ceramics

In the (Bi_{1 − x}Ce_x)VO₄ (0 ≤ x ≤ 1) system, we found that the (Bi_{1 − x}Ce_x)VO₄ (0 ≤ x ≤ 0.1) belongs to the monoclinic scheelite phase and the (Bi_{1 − x}Ce_x)VO₄ (0.7 ≤ x ≤ 1) belongs to the tetragonal zircon phase, while the (Bi_{1 − x}Ce_x)VO₄ (0.1 < x < 0.7) belongs to the mixed phases of both monoclinic scheelite and tetragonal zircon structure. Interestingly, two components with near-zero temperature coefficient of resonant frequency (TCF) appeared in this system. In our previous work, a near-zero TCF of ~+15 ppm/°C was obtained in a (Bi_0.75Ce_0.25)VO₄ ceramic with a permittivity (ε_r) of ~47.9 and a Qf (Q = quality factor = 1/dielectric loss; f = resonant frequency) value of ~18 000 GHz (at 7.6 GHz). Furthermore, in the present work, another temperature-stable microwave dielectric ceramic was obtained in (Bi_0.05Ce_0.95)VO₄ composition sintered at 950°C and exhibits good microwave dielectric properties with a ε_r of ~11.9, a Qf of ~22 360 GHz (at 10.6 GHz), and a near-zero TCF of ~+6.6 ppm/°C. The results indicate that this system might be an interesting candidate for microwave device applications.