Crystal structure, bond characteristics and microwave dielectric properties of Ce2[Zr1-x(Sr1/3B2/3)x]3(MoO4)9 (B = Ta, Sb) solid solutions

A series of Ce 2 [Zr 1- x (A) x ] 3 (MoO 4 ) 9 (A = Sr 1/3 Ta 2/3 , Sr 1/3 Sb 2/3 ; x  = 0.02, 0.04, 0.06, 0.08 and 0.10) (abbreviated as CZ 1- x T x and CZ 1- x S x ) microwave dielectric ceramics were studied systematically with respect to microstructures, sintering behaviors, crystal structures, microwave dielectric properties and infrared vibrational modes. Density measurements and scanning electron microscopy (SEM) reveal the dense and homogeneous microstructures. X-ray diffraction (XRD) results confirm the formation of solid solutions belonging to the hexagonal system with a R 3 ‾ c $R\bar{3}c$ space group, and the lattice volume increases with raising the doping content. Furthermore, the complex chemical bond theory was used to calculate the intrinsic bond parameters, and the correlations between the microwave dielectric properties and intrinsic bond parameters were established. Finally, far infrared (FIR) spectra reveal that the main polarization contribution stems from the absorptions of the phonon oscillations in these two groups of ceramics. Typically, the optimum microwave dielectric properties are achieved for CZ 0.9 T 0.1 and CZ 0.94 S 0.06 ceramics with ε r  = 10.24, Q  ×  f  = 92,009 GHz (at 9.70 GHz), τ f  = −8.84 ppm °C −1 and ε r  = 10.40, Q  ×  f  = 82,696 GHz (at 9.69 GHz) and τ f  = −8.04 ppm °C −1 , respectively. Interestingly, the CZ 0.9 T 0.1 ceramic exhibits the maximum Q  ×  f value in the ion doped Ce 2 Zr 3 (MoO 4 ) 9 ceramics while retaining a good τ f  = −8.84 ppm °C −1 .