Ion selection criteria for effective A/B site co-doping in SrTiO3: achieving comprehensive dielectric performance via synergistic pinning effect

Microwave dielectric ceramics with a high dielectric constant and low dielectric loss are essential for 5   G/6   G miniaturized communication devices; however, inherent property trade-offs hinder further performance optimization. Although A-site rare-earth or B-site composite ion doping has been employed to address this challenge in perovskites, overall performance remains limited by suboptimal A-site selection and B-site ionic mismatch. Here, we synthesized compositionally varied Sr 1-1.5 x Ce x Ti 0.98 (Zn/Mg 1/3 Nb 2/3 ) 0.02 O 3 materials through selective Ce and Zn/MgNb co-doping to simultaneously overcome sintering and dielectric performance challenges. Incorporation of small-radius A-site Ce provides additional solid-solution space for large-radius B-site Zn/MgNb, effectively promoting a single-phase composition and dense microstructure. Crucially, the valence transition of Ce, combined with its synergistic electron-pinning effect with Zn/MgNb, immobilizes free electrons and significantly suppresses Ti 4+ reduction. This synergistic interaction enhances the quality factor beyond 14,000   GHz, surpassing the Q×f values reported in previous studies. Additionally, the controlled reduction in ionic polarizability, coupled with enhanced octahedral distortion, maintains the dielectric constant above 115 while reducing the temperature coefficient from +1400 ppm/°C to +259 ppm/°C. At a doping level of 0.30, the co-doped material exhibits superior comprehensive properties: ε r = 123.9, Q×f = 14,447   GHz, and τ f = +337 ppm/°C. This study highlights the considerable potential of rational co-doping strategies to enhance material performance.