Zhenyong Cen

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.

Effect of sintering temperature on microstructure and piezoelectric properties of Pb-free BiFeO3–BaTiO3 ceramics in the composition range of large BiFeO3 concentrations

Lead-free (1-x)BiFeO3–xBaTiO3 [(1-x)BF-xBT] piezoelectric ceramics in the range of large BF concentrations were prepared by conventional oxide-mixed method at various sintering temperatures. The sintering temperatures have a significant effect on the microstructure of the ceramics, and the composition has a remarkable effect on optimal sintering temperature of the ceramics, which are closely related with piezoelectric properties. The grain size increased with increasing sintering temperature and the optimal sintering temperature increased with increasing BT content. The ceramics with x = 0.275 sintered at 990 °C exhibit enhanced electrical properties of d33 = 136pC/N and kp = 0.312 due to the polarization rotation mechanisms at MPB and desired microstructure. These results show that the ceramic with x = 0.275 is a promising lead-free high-temperature piezoelectric material.

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.