Crystal Structure and Microwave Dielectric Behaviors of Ultra-Low-Temperature Fired x(Ag0.5Bi0.5)MoO4–(1 – x)BiVO4 (0.0 ≤ x ≤ 1.0) Solid Solution with Scheelite Structure

x(Ag(0.5)Bi(0.5))MoO4-(1 - x)BiVO4 (0.0 ≤ x ≤ 1.0) ceramics were prepared by using the solid-state reaction technique. Ceramics with x < 0.10 had a monoclinic scheelite structure, while those with ≥0.10 were tetragonal scheelite solid solutions. This indicates that the phase transformation temperature of BiVO4 was lowered through the formation of a solid solution. The thermal expansion data of the x = 0.08 sample showed that the thermal expansion coefficient was increased suddenly from +8 to +15 ppm/°C at about 60.6 °C due to the phase transition. Similarly, a maximum value of microwave dielectric permittivity was revealed at about 65 °C for the x = 0.08 sample. All of the ceramics could be well sintered below 700 °C. Good microwave dielectric behaviors, with relative permittivity >75 and Q(f) > 9000 GHz, were obtained in ceramics with compositions near x = 0.10. Both the THz data and the infrared spectra were used to study the intrinsic dielectric behavior of the materials at microwave frequencies.