Domain Structure of Potassium‐Sodium Niobate Ceramics Before and After Poling

Abstract

Domain structure and domain wall motion play important roles on the piezoelectric properties of ferroelectric ceramics. In this work, the domain structure of hot‐pressed (K0.50Na0.50)NbO3 (KNN) ceramics before and after poling were studied by observing the domain patterns with an acid‐etching technique, and the extrinsic contribution to the piezoelectric properties were evaluated. It was found that the domain structure of the unpoled KNN ceramic was relatively complicated with many watermark, herringbone and zigzag patterns, while only a single set or few sets of parallel domain stripes were observed in the poled KNN ceramic, due to the domain reorientation and domain wall motion during the poling process. The average domain width changes from 200 (±10) nm before poling to 250 (±10) nm after poling. Domain configurations of “Herringbone‐Zigzag‐Watermark” and “Herringbone‐ Herringbone‐Zigzag” types observed in the unpoled KNN ceramic were then further analyzed. The extrinsic contribution to the piezoelectric properties from the domain reorientation and irreversible domain wall motion in the hot‐pressed KNN ceramic was found to be 71%, slightly higher than that of conventional sintered KNN ceramics ~68%.

Diffused Phase Transition Boosts Thermal Stability of High‐Performance Lead‐Free Piezoelectrics

“…[40] Previous works have revealed that extrinsic contribution plays an important role in KNN, especially for the compositions near PPT. [41,42] Therefore, it provides us with another easy approach to locating the PPT point T O-T by assessing the temperature and frequency dependence of piezoelectric properties. For a better understanding of the underlying mechanisms of enhanced performance in piezoelectrics, the simple but classical KNbO 3 lead-free piezoelectric is recently highlighted in both theoretical and experimental researches.…”

Domain Structure and Enhanced Electrical Properties in Sodium Bismuth Titanate Ceramics Sintered from Crystals with Different Morphologies

“…As a result, the domain width is influenced by NBT crystal morphologies, which is corresponding to the intensity change in XRD peaks as shown in Figs. (c), (f) and (i) …”

“…At present, lead‐based materials are predominant for piezoelectric applications, which imposes severe impacts on the human health and environment . As the most promising candidates to replace the lead‐based ceramics, Na 0.5 Bi 0.5 TiO 3 (NBT), K 0.5 Na 0.5 NbO 3 (KNN), and BaTiO 3 (BT) have attracted growing interest …”

“…Recently, the domain structure in KNN/BT‐based ceramics has attracted much attention, which was proved to improve their ferroelectric, dielectric, and piezoelectric properties . The domain structure in KNN‐based ceramics was changed before and after poling process, and the properties were strongly influenced by the irreversible domain wall motions . Curved domain stripes and larger average domain width were found to improve the piezoelectric properties of these ceramics .…”

Effect of Reoriented Nanodomains on Crystal Structure and Piezoelectric Properties of Polycrystalline Ferroelectric Ceramics

“…28 In the recently reported domain patterns and structure for potassium sodium niobate (KNN)-based ceramics by scanning electron microscopy (SEM), the domain patterns and a structure transition from a complicated domain structure with many watermark, (a) E=80kV herringbone, and zigzag patterns for unpoled samples to only a single set of parallel domain stripes for poled ceramics due to domain reorientation and domain wall motion, associated with increased average domain size, was observed. 31,32 On the other hand, a characterization method for ferroelectric domains has been proposed by Tan's group, 33 who established the domain structure-dielectric property relationship for BNT-BT ceramics and found that regular ferroelectric domains correspond to minimum room-temperature frequency dispersion in the dielectric constant while nanodomains lead to strong frequency dispersion.…”