Abstract: Selective ion doping is a promising method to enhance the overall performance of perovskite dielectric ceramics. However, the confrontations among the dielectric constant (ε_r), near-zero temperature coefficient of resonant frequency (TCF), and quality factor (Q × f) remain key challenges in high-performance dielectric ceramics. To leverage the trade-off conflicts, using dual-phase perovskite-based dielectric ceramic composites could be a potentially ideal solution. Unfortunately, the selected ions are hard to be doped into the perovskite phase due to the sintering temperature disparity of the two phases, thereby significantly impacting the modification effect. In this study, a “wedge” strategy was employed in a MgTiO₃-CaTiO₃ dual-phase dielectric ceramic composite by using Ce as an auxiliary dopant to realize the main Hf doping in the CaTiO₃ phase due to the lattice distortion. This strategy also harmonizes the confrontation of the sintering temperature disparity between the two components of CaTiO₃ and MgTiO₃. The Hf⁴⁺ doping level of as high as 40 mol.% with a reduced sintering temperature of over 200 °C was successfully achieved by using this “wedge” strategy. Most importantly, the trade-off conflicts among the ε_r, near-zero TCF, and Q × f have been considerably reduced and harmonized due to the successful introduction of a high dosage of Hf dopant in the CaTiO₃ phase without sacrificing the intact structure of MgTiO₃. This strategy not only sheds light on manufacturing high-performance dual-phase dielectric ceramics with trade-off conflicts of properties but also provides an innovative pathway to address the challenge of mismatch of sintering temperature for selective ion doping in multiple-phase ceramic composites.

Key words: Synergistic doping, Dual-phase structure, Microwave dielectric ceramics, Low-temperature doping, Perovskite