Lead-free BNT-based composite materials: enhanced depolarization temperature and electromechanical behavior.

Area of Science:

• Materials Science
• Solid State Chemistry
• Ceramic Engineering

Background:

• Developing lead-free piezoceramics like (Bi_0.5Na_0.5)TiO₃-BaTiO₃ (BNT-BT) for practical applications is challenging due to the trade-off between thermal stability and piezoelectric properties.
• Improved thermal stability in BNT-BT solid solutions often leads to reduced piezoelectric and electromechanical performance, hindering their widespread use.

Purpose of the Study:

• To overcome the limitations of conventional BNT-BT solid solutions by developing a composite material with enhanced thermal stability and superior piezoelectric properties.
• To investigate the role of ZnO nanoparticles in modifying the microstructure and properties of BNT-BT ceramics.
• To achieve simultaneous optimization of depolarization temperature, piezoelectricity, and electromechanical performance in lead-free piezoceramics.

Main Methods:

• Fabrication of a 0-3 type composite ceramic: 0.93(Bi_0.5Na_0.5)TiO₃-0.07BaTiO₃: 0.3ZnO (BNT-7BT:0.3ZnO).
• Characterization using X-ray Diffraction (XRD), Raman spectroscopy, and microstructure analysis to confirm the presence and distribution of ZnO nanoparticles.
• Evaluation of electromechanical properties, fatigue characteristics, thermal stability, and piezoelectric performance under varying conditions.

Main Results:

• The BNT-7BT:0.3ZnO composite exhibited a 0-3 type connectivity with ZnO nanoparticles dispersed both at grain boundaries and within the BNT-7BT lattice.
• Enhanced frequency-dependent electromechanical properties, improved fatigue resistance, and superior thermal stability were observed in the composite ceramics.
• The composite demonstrated significantly improved piezoelectric properties at a low poling field compared to the pure BNT-7BT solid solution.
• A mechanism involving ZnO-induced phase transition and a built-in electric field was proposed to explain the enhanced piezoelectric performance.

Conclusions:

• The developed BNT-7BT:0.3ZnO composite successfully overcomes the long-standing obstacle of simultaneously optimizing thermal stability and piezoelectric performance in lead-free piezoceramics.
• This study presents a novel composite engineering approach for achieving high-performance lead-free piezoceramics.
• The findings open new avenues for the practical application of BNT-based and other lead-free piezoelectric materials.