(1-x)(Na₀.₅Bi₀.₅)TiO₃-xCaTiO₃ ceramics: Investigating structural and microstructural features for enhanced dielectric...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Dielectric Materials

Background:

• Lead-free piezoelectric ceramics are crucial for sustainable electronic devices.
• The (Na₀.₅Bi₀.₅)TiO₃-CaTiO₃ system offers a promising lead-free alternative.
• Understanding phase transitions and electrical properties is key to optimizing performance.

Purpose of the Study:

• To investigate the effect of CaTiO₃ (CT) doping on the phase, structure, and electrical properties of (1-x)(Na₀.₅Bi₀.₅)TiO₃ (NBT) lead-free piezoelectric ceramics.
• To identify the optimal composition for enhanced dielectric properties.
• To analyze the relationship between structure, phase, and electrical behavior.

Main Methods:

• Solid-state reaction route for synthesis of NBT-CT ceramics with varying compositions (x = 0.0 to 0.20).
• X-ray diffraction (XRD) with Rietveld refinement for phase identification and structural analysis.
• Scanning electron microscopy (SEM) for microstructure and grain size analysis.
• Dielectric measurements to determine permittivity and phase transition temperatures.
• Williamson-Hall plot analysis for particle size estimation.
• Analysis of charge density distribution to understand CT phase impact.
• AC conductivity measurements for thermal activation analysis.

Main Results:

• A morphotropic phase boundary (MPB) involving rhombohedral (R3c) and orthorhombic (Pnma) structures was observed near x = 0.10.
• Rietveld refinement and SEM confirmed pure phase formation and provided grain size information.
• Particle sizes were estimated between 131.87 nm and 136.54 nm using Williamson-Hall plots.
• Relative permittivity increased with Ca²⁺ addition, peaking at the MPB (x=0.10).
• Diffuse phase transitions (diffusivity 1.5-1.8) and a downward shift in depolarization temperature (Td) were observed.
• Excellent dielectric properties at x = 0.10 were attributed to the coexistence of rhombohedral and orthorhombic phases and optimal particle size.
• Conduction mechanism was identified as thermally activated.

Conclusions:

• The (1-x)NBT-xCT system exhibits tunable phase structures and electrical properties with varying CaTiO₃ content.
• The morphotropic phase boundary at x = 0.10 is critical for achieving superior dielectric performance in these lead-free piezoelectric ceramics.
• The findings provide valuable insights for designing high-performance lead-free piezoelectric materials.