Na2Ti3O7 Ceramics: A Review on Doping-Induced Structural, Dielectric, And Charge Transport Dynamics

Abstract

In this study, layered sodium tri-titanate (Na2Ti3O7) ceramics doped with 1.0 mol % transition metals (copper, iron, and manganese) were synthesised using a solid-state reaction method. X-ray diffraction confirmed that all samples retained a single-phase monoclinic crystal structure. Replacing the smaller host Ti⁴⁺ ions with larger dopant cations (Cu²⁺, Mn²⁺/³⁺, Fe³⁺) expanded the interlayer spacing, shifting the primary reflection peaks to lower 2θ angles. Temperature-dependent dielectric testing at 1 MHz revealed that doping creates charge-compensating oxygen vacancies, which lower the activation energy for dipole rotation and cause relaxation peak temperatures to drop systematically (Cu: 600 K < Fe: 612 K < Mn: 622 K < Pure: 635 K). Copper (Cu²⁺) doping generated the highest relative permittivity (ε' ≈ 770), though with increased energy losses. Electrical conductivity studies demonstrated four distinct temperature regions, showing a transition from low-temperature electronic hopping between Ti³⁺/Ti⁴⁺ states to high-temperature fast Na⁺ ion flow quickly through the layer pathways. Overall, these small chemical changes provide an effective way to improve material performance. They offer capable opportunities for developing advanced materials for sodium-ion batteries and high-temperature energy storage applications.