Effects of AC- and DC-bias field poling on piezoelectric properties of Bi-based ceramics

Abstract

The structural and electrical properties of 0.75BiFeO 3 0.25BaTiO 3 (BF25BT) ceramics, with and without heat treatment, were investigated. The polished and cut BF25BT ceramics were thermally annealed at 800°C for 20 h and then quenched in water at room temperature (heat-treated ceramics). The PE hysteresis loop and SE curve were significantly improved after the heat treatment process. Meanwhile, the leakage current density at an electric field of 50 kV/cm was reduced from 4.847 © 10 ¹7 (as-sintered ceramics) to 3.213 © 10 ¹8 A/cm 2 (heattreated ceramics). The heat-treated ceramics was poled at 120°C with applying a DC-bias field of 50 kV/cm, and the maximum phase angle was ¹39°, which was evaluated from the analysis of frequency-dependence of impedance and phase angle. Because of the small maximum phase angle obtained by poling under DC-bias field alone, the poling process was modified; that is, an AC-bias field was applied prior to the DC-bias field poling. The ceramics poled with the modified poling procedure exhibited the maximum phase angle of 63°. The appreciable increase of the maximum phase angle suggested the higher degree of domain alignment than that of its counterpart, and the effect was explained in terms of improved domain switching. The piezoelectric constant d 33 was increased twice with adopting the modified poling process, which signifies that poling with both AC-and DC-bias field is highly effective in the lead-free Bi-based systems.

Enhancement of Piezoelectricity by Novel Poling Method of the Rare‐Earth Modified BiFeO3–BaTiO3 Lead‐Free Ceramics

“…[ 53 ] However, the domain pinning effect could be relaxed by alternating current poling (ACP) as a result the d 33 values are improved. [ 54,55 ] Therefore, a bipolar triangular voltage was applied for 10 3 cycles at 1 Hz before the DC‐bias poling. It was very interesting to note that a significant improvement occurred in the d 33 for all samples after AC‐bias and DC‐bias poling as shown in Figure 10c.…”

Lead-Free BiFeO3-Based Piezoelectrics: A Review of Controversial Issues and Current Research State

“…The piezoelectric coefficient and phase angle were measured after the direct current poling (DCP) process. However, a few reports have focused on the phase angle, which can provide important information as a measure of whether the completed domain switching by the poling process is carried out properly [103]. Recently, ultrahigh dielectric and piezoelectric properties in relaxor-PT crystals have been achieved by alternating current poling (ACP) rather than the conventional DCP process [104,105].…”

“…Recently, ultrahigh dielectric and piezoelectric properties in relaxor-PT crystals have been achieved by alternating current poling (ACP) rather than the conventional DCP process [104,105]. A study has been conducted to improve not only the phase angle but also the piezoelectric coefficient in the BF-BT system by combining the ACP and DCP processes [103]. However, this is a preliminary stage, and systematic ACP research is necessary to simultaneously monitor piezoelectric activity and phase angle.…”

A Review of a Good Binary Ferroelectric Ceramic: BaTiO3–BiFeO3

“…The ceramic presented better piezoelectric performance when an alternating current bias field was loaded before the direct current bias field poling. 55 How do we assess the degree of polarization (reorientation degree of domains)? The study of impedance |Z| and phase angle θ between the resonance frequency (f r ) and the antiresonance frequency (f a ) can achieve this goal.…”

“…There are also differences in the polarization through DC or AC power supply. The ceramic presented better piezoelectric performance when an alternating current bias field was loaded before the direct current bias field poling . How do we assess the degree of polarization (reorientation degree of domains)?…”