Crystal Structure, Infrared Spectra, and Microwave Dielectric Properties of Temperature-Stable Zircon-Type (Y,Bi)VO₄...

A series of (Bi_1- Y )VO₄ (0.4 ≤ x ≤ 1.0) ceramics were synthesized using the traditional solid-state reaction method. In the composition range of 0.4 ≤ x ≤ 1.0, a zircon-type solid solution was formed between 900 and 1550 °C. Combined with our previous work (scheelite monoclinic and zircon-type phases coexist in the range of x < 0.40), a pseudobinary phase diagram of BiVO₄-YVO₄ is presented. As x decreased from 1.0 to 0.40, the microwave permittivity (ε_r) of (Bi_1- Y )VO₄ ceramics increased linearly from 11.03 to 30.9, coincident with an increase in the temperature coefficient of resonant frequency (TCF) from -61.3 to +103 ppm/°C. Excellent microwave dielectric properties were obtained for (Bi_0.3Y_0.7)VO₄ sintered at 1025 °C and (Bi_0.2Y_0.8)VO₄ sintered at 1075 °C with ε_r ∼ 19.35, microwave quality factor (Qf) ∼ 25 760 GHz, and TCF ∼ +17.8 ppm/°C and ε_r ∼ 16.3, Qf ∼ 31 100 GHz, and TCF ∼ -11.9 ppm/°C, respectively. Raman spectra, Shannon's additive rule, a classical oscillator model, and far-infrared spectra were employed to study the structure-property relations in detail. All evidence supported the premise that Bi-based vibrations dominate the dielectric permittivity in the microwave region.