Understanding the piezoelectric properties in potassium-sodium niobate-based lead-free piezoceramics: Interrelationship between intrinsic and extrinsic factors

Abstract

Lead zirconate titanate (PZT) based ceramics are currently enjoying a wide use in piezoelectric devices despite lead toxicity. Due to growing environmental concerns, the attention on piezoelectric ceramics has been moving to lead-free materials, in particular to (K,Na)NbO 3-based ceramics. Here we report a systematic evaluation of the effects of the compositional modifications on [(K0.44Na0.52Li0.04)[(Nb0.86Ta0.10Sb0.04)1-xZr5x/4]O3 lead-free piezoceramics. We show that an interrelationship between the intrinsic and extrinsic factors is the linchpin for the development of good piezoelectric properties. Hence, the stabilization of the tetragonal symmetry on the orthorhombic-tetragonal polymorphic phase boundary facilities the poling process of the system, thereby enhancing the piezoelectric response. Additionally, the microstructure appears to be related to the piezoelectric properties; i.e., the improved piezoelectric properties correlate to the increase in grain size. The results of this work could help to understand the origin of piezoelectricity in potassium-sodium niobate-based ceramics.

Temperature stability and electrical properties in La‐doped KNN‐based ceramics

“…Indeed, as x increases, the mean grain size also increases from 1.37 μm ( x = 0) to 2.32 μm ( x = 0.2), and then decreases to 0.22 μm ( x = 0.8) (Figure E‐H). Previous studies reported that an increase in grain size can improve the ferro/piezoelectric properties, and that a reduced grain size can strengthen the coupling effect between grains and grain boundaries, which hinders switching of the domains . In this work, an easy domain switching is clearly observed in ceramics with x = 0.2 (Figure ), due to the R‐T phase boundary and the addition of La 3+ .…”

“…Previous studies reported that an increase in grain size can improve the ferro/piezoelectric properties, and that a reduced grain size can strengthen the coupling effect between grains and grain boundaries, which hinders switching of the domains. 37 In this work, an easy domain switching is clearly observed in ceramics with x = 0.2 (Figure 7), due to the R-T phase boundary and the addition of La 3+ . Therefore, the fatigue-free behavior in these ceramics is mainly attributed to the dense microstructure and easy domain switching.…”

Enhanced piezoelectricity and temperature stability in LaFeO3‐modified KNN‐based lead‐free ceramics

“…The ε r value exhibited an increasing trend first and then decreased when x ≥ 0.008, while the dielectric loss showed the opposite trend. For piezoelectric ceramics, both the intrinsic polarization rotation and the extrinsic domain wall contribution contributed to the piezoelectric response . In general, samples with O‐T coexisting phases that possess a high T‐phase fraction demonstrate a high piezoelectric performance due to the large lattice distortion in the T phase.…”

“…For piezoelectric ceramics, both the intrinsic polarization rotation and the extrinsic domain wall contribution contributed to the piezoelectric response. 30 In general, samples with O-T coexisting phases that possess a high T-phase fraction demonstrate a high piezoelectric performance due to the large lattice distortion in the T phase. In this study, the gradual shift of T O-T induced by the incorporation of LaFeO 3 could partially contribute to the enhanced d 33 or k p when x ≤ 0.006, while the drastic decrease in the piezoelectric performance with x ≥ 0.008 was ascribed to the phase transition to a pseudocubic phase.…”

Electrocaloric behavior and piezoelectric effect in relaxor NaNbO3‐based ceramics

“…It is difficult to find the lead‐free piezoelectric ceramics with real “MPB” which always leads to optimized temperature stability of electrical properties. Poor temperature stability of lead‐free piezoceramics is almost attributed to the characteristics of polymorphic phase boundary . Fortunately, Zuo et al claimed that MPB can be constructed in NaNbO 3 ceramics by chemical modifications, which benefits the enhancement of piezoelectricity and temperature stability .…”