As research on lead−free energy storage materials advances, high−performance substrates and their modification methods have been continuously explored. In NaNbO₃–based energy storage ceramics, low polarization limits the enhancement of energy storage performance. This study utilized defect engineering design to prepare (1–x)NaNbO₃-xSr(Fe_1/3Sb_2/3)O₃ ceramics with core–shell structure through a Fe/Sb dual oxidation state variable element synergistic regulation strategy. The goal is to enhance ΔP and optimize E_b of ceramics by adjusting the content of vacancy defects and phase structure, so that ceramics can achieving high energy storage characteristics. A W_rec of 6.4 J/cm³ and η of 80% at 645 kV/cm were achieved in NaNbO₃–based ceramic. Additionally, based on this study, we performed a detailed analysis of the origin of high ΔP and the influence of defect structures on E_b, with the aim of providing a new reference for development and research of high–performance lead–free energy storage ceramics.

Microwave dielectric ceramics should be improved to advance mobile communication technologies further. In this study, we prepared Sr_1+xY₂O_4+x (x = 0–0.04) ceramics with nonstoichiometric Sr²⁺ ratios based on our previously reported SrY₂O₄ microwave dielectric ceramic, which has a low dielectric constant and an ultrahigh quality factor (Q value). The ceramic exhibited a 33.6% higher Q-by-frequency (Q×f) value (Q ≈ 12,500) at x = 0.02 than SrY₂O₄. All Sr_1+xY₂O_4+x (x = 0–0.04) ceramics exhibited pure phase structures, although variations in crystal-plane spacings were observed. The ceramics are mainly composed of Sr–O, Y1–O, and Y2–O octahedra, with the temperature coefficient of the resonant frequency (τ_f) of the ceramic increasing with Y2–O octahedral distortion. The ceramic comprises uniform grains with a homogeneous elemental distribution, clear grain boundaries, and no obvious cavities at x = 0.02. The Sr_1+xY₂O_4+x (x = 0–0.04) ceramics exhibited good microwave dielectric properties, with optimal performance observed at x = 0.02 (dielectric constant (ε_r) = 15.41, Q×f = 112,375 GHz, and τ_f = −17.44 ppm/℃). The τ_f value was reduced to meet the temperature-stability requirements of 5G/6G communication systems by adding CaTiO₃, with Sr_1.02Y₂O_4.02+2wt%CaTiO₃ exhibiting ε_r = 16.14, Q×f = 51,004 GHz, and τ_f = 0 ppm/℃. A dielectric resonator antenna prepared using Sr_1.02Y₂O_4.02+2wt%CaTiO₃ exhibited a central frequency of 26.6 GHz, with a corresponding gain and efficiency of 3.66 dBi and 83.14%, respectively. Consequently, Sr_1.02Y₂O_4.02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band (24.5–27.5 GHz) applications.