Extremely reduced loss tangent with retaining ultra high dielectric permittivity in Mg(2+)-doped La(1.9)Sr(0.1)NiO(4) ceramics

An extremely reduced loss tangent while retaining ultrahigh dielectric permittivity can be successfully obtained in La(1.9)Sr(0.1)NiO(4) ceramics by doping with Mg(2+) ions. A single phase of La(1.9)Sr(0.1)NiO(4) was detected in all the sintered ceramics, while the lattice parameters increased with increasing doping concentration, indicating that Mg(2+) ions can enter the Ni(2+) sites. A highly dense microstructure is achieved. Microstructural analysis revealed that Mg(2+) ions disperse well in the microstructure of La(1.9)Sr(0.1)NiO(4) ceramics. Interestingly, ultra–high dielectric permittivity of approximately 8.11 × 10(5) at 1 kHz is achieved in the La(1.9)Sr(0.1)Ni(0.6)Mg(0.4)O(4) ceramic, while the loss tangent is significantly reduced by two orders of magnitude compared to the undoped La(1.9)Sr(0.1)NiO(4) ceramic. The DC conductivity significantly decreased by three orders of magnitude. The giant dielectric responses are described by Maxwell–Wagner polarization and small polaron hopping mechanisms. Thus, the significant reduction in the loss tangent can be attributed to the significantly enhanced resistance of the grain boundaries.