Effects of Mg2+ doping ions on giant dielectric properties and electrical responses of Na1/2Y1/2Cu3Ti4O12 ceramics

Abstract Influences of Mg 2+ doping ions on electrical and giant dielectric properties of Na 1/2 Y 1/2 Cu 3- x Mg x Ti 4 O 12 ( x =0–0.3) ceramics prepared by a conventional solid state reaction method were systematically studied. Mg 2+ doping ions were homogeneously dispersed in the microstructure and caused a large increase in the mean grain size from 11.0 to 88.4 µm as Mg 2+ concentration was increased from x =0 to 0.3. This resulted in a reduction of the breakdown voltage (from 3002 to 537 V cm −2 ) and nonlinear coefficient (from 6.79 to 5.40), indicating the importance of microstructure in controlling the nonlinear current–voltage properties of Na 1/2 Y 1/2 Cu 3 Ti 4 O 12 . The grain and grain boundary responses were characterized by admittance and impedance spectroscopy analyses, respectively. X–ray absorption near edge structure and X–ray photoelectron analyses confirmed the presence of Cu+, Cu 3+ , and Ti 3+ ions in Na 1/2 Y 1/2 Cu 3− x Mg x Ti 4 O 12 ceramics, indicating the complex mechanisms of conduction exist inside the grains. Substitution of Mg 2+ resulted in a small decrease in conduction inside the grains, which may primarily be attributed to the reduction of the Ti 3+ concentration. Reduced loss tangent (≈0.036) and enhanced permittivity (≈2.02×10 4 ) with better temperature stability were achieved in the Na 1/2 Y 1/2 Cu 2.9 Mg 0.1 Ti 4 O 12 ceramic compared to the undoped sample. The dielectric relaxation behavior can be well described using the Maxwell–Wagner relaxation model based on the internal barrier layer capacitor structure.