Extremely reduced loss tangent with retaining ultra high dielectric permittivity in Mg2+-doped La1.9Sr0.1NiO4 ceramics

Abstract

An extremely reduced loss tangent while retaining ultrahigh dielectric permittivity can be successfully obtained in La1.9Sr0.1NiO4 ceramics by doping with Mg2+ ions. A single phase of La1.9Sr0.1NiO4 was detected in all the sintered ceramics, while the lattice parameters increased with increasing doping concentration, indicating that Mg2+ ions can enter the Ni2+ sites. A highly dense microstructure is achieved. Microstructural analysis revealed that Mg2+ ions disperse well in the microstructure of La1.9Sr0.1NiO4 ceramics. Interestingly, ultra–high dielectric permittivity of approximately 8.11 × 105 at 1 kHz is achieved in the La1.9Sr0.1Ni0.6Mg0.4O4 ceramic, while the loss tangent is significantly reduced by two orders of magnitude compared to the undoped La1.9Sr0.1NiO4 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.

Keywords

• Nickelate
• Giant dielectric properties
• Loss tangent
• DC conduction
• Maxwell−Wagner polarization