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

A series of (Bi1-xYx)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 degrees 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 (epsilon(r)) of (Bi1-xYx)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/degrees C. Excellent microwave dielectric properties were obtained for (Bi0.3Y0.7)VO4 sintered at 1025 degrees C and (Bi0.2Y0.8)VO4 sintered at 1075 degrees C with epsilon(r) similar to 19.35, microwave quality factor (Qf) similar to 25 760 GHz, and TCF similar to +17.8 ppm/degrees C and epsilon(r) similar to 16.3, Qf similar to 31 100 GHz, and TCF similar to -11.9 ppm/degrees 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.