Effect of Ca/Zr co-substitution on microstructure and microwave dielectric characteristics of CaSmAlO₄-based ceramics

Ca_1+xSm_1−xAl_1−xZr_xO₄ (x=0.1, 0.2, 0.3, 0.4) microwave ceramics in the lamellar perovskite structure were fabricated by the traditional solid-phase synthesis method. The effect of the Ca/Zr co-substitution on the crystal structure, microstructure, and dielectric characteristics of the microwave ceramics were investigated by X-ray diffraction (XRD), Raman spectra, electron backscatter diffraction (EBSD), energy dispersive spectroscopy (EDS), and vector network analysis (VNA). In the results, the cell parameters (a, c), cell volume (V_cell), and theoretical polarizability (α_theo) increase with the increase of x, leading to the increase of the dielectric constant (ε_r) and resonant frequency temperature coefficient (τ_f); meanwhile, a moderate amount of CaO secondary phases can improve the quality factor (Q×f). Ca_1.2Sm_0.8Al_0.8Zr_0.2O₄ (x=0.2) ceramics show the excellent microwave performance as ε_r=20.16, Q×f=72489, and τ_f = −3.46×10⁻⁶·℃⁻¹.