Effect of B-site complex substitutions on orthorhombic distortion and microwave dielectric properties of Ca(Zr_0.95Ti_0.05)O₃ perovskites

Moderate permittivity (e_r), high-quality factor (Q = 1/tand) and near-zero temperature coefficient of the resonant frequency (t_f) are key parameters in the advancement of microwave dielectric devices. However, the inherent inverse correlation between e_r and Q × f values poses a challenge in designing high-permittivity microwave ceramic materials. To address this challenge, complex-ion-modified ceramics have attracted attention for the development of new microwave dielectric materials. In this study, (1 - x)Ca(Zr_0.95Ti_0.05)O₃–xCa(Zn_1/3Nb_2/3)O₃ (0 r x r 0.3) perovskite microwave dielectric ceramics were prepared using a solid state reaction method. Structural characterization using advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy provides a comprehensive insight into the profound effects of (Zn_1/3Nb_2/3)⁴⁺ complex-ion substitution. These effects are elucidated in terms of the lattice parameters, grain size, flexural strength, degree of orthorhombic distortion and vibrational modes, highlighting the modified structural properties achieved by this substitution strategy. As substitution increases, the degree of orthogonal distortion of the samples decreases, which also has a significant effect on the microwave dielectric properties. Here, the excellent microwave dielectric properties with e_r = 33.8, Q × f = 33470 GHz and a near-zero t_f value (+3.7 ppm 1C^-1) were obtained when x = 0.3 M. These results provide a promising avenue for achieving tunable microwave dielectric properties of Zr-based perovskite ceramics.