Defect dipole engineering induced by Cobalt(II) doping enables ultralow dielectric loss in Zn2SiO4 ceramics

Abstract

Tunnel-structured zinc orthosilicate (Zn2SiO4) is a promising low-loss dielectric ceramic, yet further suppression of dielectric dissipation requires effective regulation of its local defect structure. Herein, pristine Zn2SiO4 and Ni2+, Co2+, and Mn2+ singly doped ceramics are prepared from chemically homogeneous precursors obtained by solvent evaporation. This synthesis route promotes uniform transition-metal incorporation at Zn lattice sites and enables controlled perturbation of the tetrahedral framework. Although Ni, Co, and Mn substitution all induce lattice distortion and defect formation, their dielectric effects are markedly different. In contrast to Ni and Mn, which introduce additional relaxation loss, Co selectively lowers dielectric dissipation. The Co-doped ceramic exhibits an ultralow tanδ of 7.3 × 10−5 at 1 MHz with an εr of 9.2 at room temperature, nearly one order of magnitude lower than that of pristine Zn2SiO4. Electron paramagnetic resonance, X-ray photoelectron spectroscopy, and density functional theory calculations suggest that tetrahedrally coordinated Co2+ may enhance localized electron trapping and stabilize oxygen-vacancy-related defect complexes. These localized defect centers may suppress long-range carrier migration and weaken Maxwell-Wagner interfacial polarization, thereby reducing dielectric loss while maintaining a relatively high dielectric constant. This work establishes dopant-stabilized defect localization as an effective strategy for designing ultralow-loss silicate dielectric ceramics.