Dielectric and piezoelectric enhancement in lead-free Bi0.5Na0.5TiO3 ceramics by incorporating BaTiO3

Description

This study presents a simple and cost-effective approach to enhance the dielectric and piezoelectric properties of Bi₀.₅Na₀.₅TiO₃ (BNT) by incorporating BaTiO₃ (BT) via high-energy ball milling. X-ray diffraction confirmed the formation of BNT–xBT solid solutions and a structural transition from rhombohedral to tetragonal symmetry. Frequency-dependent dielectric measurements showed a notable increase in relative permittivity, reaching 1750, over twice that of undoped BNT. This enhancement is linked to the formation of polar nanoregions (PNRs), which boost dielectric susceptibility through localized polarization. Temperature-dependent analysis revealed a broadened permittivity peak and diffuse phase transition, indicating disrupted long-range ferroelectric order and growing PNR activity. Polarization–electric field (P–E) loops showed a reduction in coercive field from ~ 60 kV/cm in pure BNT to ~ 23 kV/cm in BNT-BT modified samples, due to the coexistence of PNRs and ferroelectric domains, facilitating polarization switching and resulting in slim hysteresis loops. The piezoelectric coefficient d33 improved from pC/N (x = 0) to 120, 158, and 165 pC/N for x = 0.08, 0.09, and 0.10, respectively, attributed to changes in the crystal structure and increased domain mobility. These findings highlight the potential of BNT–xBT obtained by high-energy ball milling as a promising lead-free piezoelectric material for advanced electromechanical applications.

Steps to reproduce

BNT was synthesized using high–purity raw materials: Na2CO3 (Sigma Aldrich, 99 %), TiO2 (Sigma Aldrich, 99 %) and Bi2O3 (Sigma Aldrich, 99 %). The reagents were weighed according to the stoichiometric ratio indicated in Eq. (1) to obtain a total mass of 5 g. The mixture was placed in a 50 cm3 steel vial along with 12.7 mm diameter steel balls, using a ball-to-powder weight ratio of 10:1. The high-energy milling process was carried out at room temperature in an air atmosphere, without using any process control agent. High-energy ball milling was performed using a shaker miller (SPEX model 8000D) for 5 h, with 30 min rest intervals after every 90 min of milling to avoid overheating. The milled powders were submitted to annealing at 1073 K for 2 h to facilitate the diffusion process before the sintering.

Institutions

• Universidad Autónoma del Estado de Hidalgo

  Hidalgo, Pachuca
• Instituto Politécnico Nacional

  Mexico City, Mexico City

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