[Formula: see text] (SLTO) ceramics ([Formula: see text] = 0.05, 0.10, 0.15) were prepared with giant dielectric constant by the traditional solid-state method at 1350[Formula: see text]C. The temperature dependence of the dielectric constant was obtained at the temperature ranging from 29[Formula: see text]C to 500[Formula: see text]C and the frequency ranging from 2 kHz to 2 MHz. Two sets of relaxation peaks appear in the low temperature (region I) and the high temperature (region II), respectively. For region I, we conclude that the relaxation behavior is related to the oxygen vacancy migration. For region II, the two relaxation processes are caused by grain boundary for high frequency and Sr or Ti defects at grain interior for low frequency. With the doping amount reaching 0.15, the relaxation peaks disappear and become a common phase transition because of the aggravation of lattice distortion. These possible physical mechanisms of two sets of relaxation peaks are briefly discussed.

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We synthesized lead-free ([Formula: see text]CaZrO3–[Formula: see text]SrTiO3 solid-solution ceramics and studied their structure, dielectric and energy storage properties. X-ray diffraction and scanning electron microscope reveal the microstructure of the samples. A high temperature dielectric relaxation behavior at the temperature ranges of 200[Formula: see text]C–550[Formula: see text]C is found for [Formula: see text], 0.5 and 0.7 samples. We explore that the origin of high temperature dielectric relaxation behavior is related to the migration of oxygen vacancies by Arrhenius law and oxygen treatment experiment. Moreover, with the increase of SrTiO3 content, the 0.3CaZrO3–0.7SrTiO3 exhibits high dielectric constant ([Formula: see text] at 1 kHz), low dielectric loss ([Formula: see text] at 1 kHz), good energy density ([Formula: see text] J/cm[Formula: see text] and high efficiency ([Formula: see text]%) simultaneously, and the possible causes of energy storage behavior dependence are analyzed in detail.