Weidong Zeng

Origin of high piezoelectric activity in perovskite ferroelectric ceramics

Dense (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNT-BTx%, x = 3, 5, 6, and 7) ceramics exhibit large piezoelectricity for electrical poling below coercive fields. In particular, the piezoelectric activity and permittivity frequency dispersion have been found to be closely related. The significantly increased piezoelectric constant and sharply decreased permittivity frequency dispersion are observed to occur for poled ceramics under the critical poling electrical fields. These results suggest that the high piezoelectric response stems from poling electrical fields-induced-ordered nanodomains.

Normal-to-relaxor ferroelectric phase transition and electrical properties in Nb-modified 0.72BiFeO3-0.28BaTiO3 ceramics

Perovskite-type 0.72BiFeO3-0.28BaTi1-xNbxO3 (BF-BTNx) ceramics were fabricated via a conventional oxide-mixed method. The phase transition behaviors, composition-dependent grain size, dielectric, ferroelectric and piezoelectric properties were investigated as a function of Nb content. The temperature dependence of dielectric permittivity showed that thermally driven normal to diffuse ferroelectric transition and Nb-doping induced normal to relaxor ferroelectric transition. Simultaneously, the butterfly shape to sprout shape transition for electric-field-induced strain curves and saturation to slim P-E hysteresis loops transition were associated with the normal-to-relaxor transition. And the low hysteresis strain curves for relaxor BF-BTNx ceramics indicated that the system was a promising candidate for high precision actuation applications. In addition, XRD results revealed that Nb-doping induced a structural transition from rhombohedral phase to pseudo-cubic phase, which may be the origin of normal-to-relaxor ferroelectric phase transition.

A new insight into structural complexity in ferroelectric ceramics

The structure of the ferroelectrics has been widely studied in order to pursuing the origin of high electromechanical responses. However, some experiments on structure of ferroelectrics have yielded different results. Here, we report that the controversial phase structure is due to the adaptive diffraction of nanodomains which hides the natural crystal structure, and the electric-field-induced phase transition is that the natural crystal structure reappears due to the coalescent nanodomains or ordering nanodomains by applying a high electric field. The temperature dependence of dielectric constant with different measurement frequencies and X-ray diffraction (XRD) patterns of unpoled, poled, and annealing after poled ceramics in Bi0.5Na0.5TiO3–BaTiO3 (BNT–BT) ceramics authenticate the statement. These results provide a new insight into the origin of structural complexity in ferroelectric ceramics, which is related to the key role of nanodomains.

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

It has been widely accepted that electric fields induce a reversible structural phase transition and thus yield giant piezoelectric responses in ferroelectric ceramics. Based on detailed measurements of polycrystalline (Li0.5Nd0.5)2+-modified 0.95Bi0.5Na0.5TiO3-0.05BaTiO3 ceramics, we demonstrate in this study that coherent diffraction from nanodomains in ferroelectric ceramics masks the real crystal structure. The observed electric-field-induced phase transformation behavior is a consequence of relaxor-to-ferroelectric transformation caused by changes in the coherence length of the nanodomains. A driving mechanism of the structure–property relationship in which high piezoelectric properties originate from correlated ordering of nanodomains during poling is proposed.

Effect of domains configuration on crystal structure in ferroelectric ceramics as revealed by XRD and dielectric spectrum

It is well known that domains and crystal structure control the physical properties of ferroelectrics. The ex-situ electric field-dependent structural study, carried out in unpoled/poled crushed powder and bulk samples for

Tailoring antiferroelectricity with high energy-storage properties in Bi0.5Na0.5TiO3–BaTiO3 ceramics by modulating Bi/Na ratio

(\hbox {Li}_{0.5} \hbox {Nd}_{0.5})^{2+}

Ferroelectric‐quasiferroelectric‐ergodic relaxor transition and multifunctional electrical properties in Bi0.5Na0.5TiO3‐based ceramics

(Li0.5Nd0.5)2+ modified 0.95