Dielectric abnormality and high-permittivity microwave dielectric properties of SrO-TiO2-CeO2 solid solution

Abstract

The SrO-TiO2-CeO2 (Sr1−1.5×CexTiO3, SCTO, 0 ≤ x ≤ 0.2, sintered in N2) solid solution exhibited the existence of dielectric abnormality/anomaly (for polished samples) and high-permittivity microwave dielectric properties (for unpolished samples). X-ray diffraction (XRD) and Rietveld refinement, along with high-resolution transmission electron microscopy (HRTEM), indicated the evidence of cubic like structure. The SEM-EDX maps demonstrated the formation of a complete solid solution, which further support the XRD results. X-ray photoelectron spectroscopy (XPS) analysis showed mixture of ion valence states upon lattice defects formation. The activation of the TO2/TiO4 polar bands usually described a relaxor-type-dielectric anomaly. The ε′-T curve, together with the polar nature measurements exhibited hysteresis loops, indicating that ceria ions induced weak relaxor behavior. The observed Q×f values were primarily dependent on the lattice defects and Ti3+ cations. The temperature coefficient of resonant frequency (τf) shifted gradually from more positive (+1321 ppm/°C) to less positive (+539 ppm/°C) values with a rise of Ce content (x). The unpolished sample with x = 0.2 exhibited a high permittivity microwave dielectric properties with εr = 182, τf = +539 ppm/°C, and Q×f = 668 GHz.