Unveiling the dynamics of phase-transition from ferroelectric to relaxor behavior in Nd-doped BNT-based lead-free piezoelectric ceramics

초록

In this study, lead-free 0.852Bi0.5Na0.5TiO3-0.12Bi0.5K0.5TiO3-0.028BaTiO3 (BNKBT 85.2/12/2.8) ceramics were synthesized using the conventional mixed oxide method, with Nd3+ doping at concentrations of 0.00, 0.25, 0.50, 0.75, 1.00, and 2.00 mol%. The research focused on the phase transition from ferroelectric to relaxor and the associated electromechanical properties. X-ray diffraction (XRD) analysis confirmed the successful incorporation of Nd3+ into the lattice, forming a perovskite phase and indicating the coexistence of multiple phases in the morphotropic phase boundary (MPB) region. The transition from ferroelectric to relaxor was observed in the polarization-electric field (P-E) and strain-electric field (S-E) loops. Pure samples exhibited ferroelectric behavior, with a relatively square P-E loop and a butterfly-shaped S-E loop. At 0.5 mol% Nd3+, a pinched P-E loop and a significant negative strain in the S-E loop were observed. At 2.0 mol% Nd3+, the ceramics demonstrated relaxor characteristics, with a thin P-E loop and minimal negative strain in the S-E loop. The optimal piezoelectric coefficient (d33), remnant polarization (Pr), and dielectric constant (epsilon r) were found at 0.5 mol% Nd3+, reaching 243 pC N-1, 36.61 mu C cm-2, and 1814.54, respectively. The highest value of 761 pm V-1 was observed at 2.0 mol% Nd3+, indicating dominant relaxor behavior. This study highlights the significant influence of Nd3+ doping on the phase transition and electromechanical properties of BNKBT ceramics, underscoring their potential as lead-free alternatives for sensor and actuator applications.

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