The possibility of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 (PNN-PT-PZ) pseudoternary system across the morphotropic phase boundary (MPB). On cooling, the PNN-PT-PZ system in the tetragonal-rich side of the MPB underwent a spontaneous transition from a relaxor to a normal ferroelectric state. This observation was explained in terms of a thermally driven transformation from an ensemble of polar microregions to normal long-range ferroelectric domains (micro-macrodomain switching). The relaxor-normal ferroelectric transition was further correlated with the rhombohedral-tetragonal first-order phase transition. Increasing the relative content of PbZrO3 enhanced dielectric dispersion characteristics but weakened the extent of relaxor-normal transition. This observation was explained by the enhanced 1:1 Nb-Zr short-range ordering and the breaking of the translational invariance of the ferroelectrically active BO6 octahedra with increasing content of PbZrO3.
The piezoelectric properties of (1−x)(Bi 0.5 Na 0.5 ) TiO 3 -xBaTiO 3 ceramics were reported and their piezoelectric properties reach extreme values near the MPB (about x= 0.06). The X-ray analysis of (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 ceramics for all compositions exhibited a pure perovskite structure without any secondary phase. Within a certain ratio of contents, the co-doped ceramics enhanced piezoelectric coefficient (d 33 ), lowered the dielectric loss, and increased the sintered density. The temperature dependence of relative dielectric permittivity (K 33 T ) reveals that the solid solutions experience two phase transitions, ferroelectric to antiferroelectric and anti-ferroelectric to relaxor ferroelectric, which can be proven by P-E hysteresis loops at different temperatures. In addition, the specimen containing 0.04/ 0.01 wt.% CaO/MnO showed that the coercive field E c was a minimum value of 26.7 kV/cm, while the remnant polarization P r was a maximum value of 38.7 μC/cm 2 , corresponding to the enhancement of piezoelectric constant d 33 of 179 pC/N, electromechanical coupling factor k p of 37.3%, and relative dielectric permittivity K 33 T of 1137. (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 ceramics co-doped with CaO/ MnO were considered to be a new and promising candidate for lead-free piezoelectric ceramics owing to their excellent piezoelectric/dielectric properties, which are superior to an un-doped BNBT system.
This paper describes micromachined piezoelectric microspeakers that can produce an audible signal supplied from an MP3 player through the use of 5V peak-to-peak signal amplification circuit modules. The Sound Pressure Level (SPL) of the fabricated microspeakers is higher than that of previous results even though the input voltage is reduced. The success of this technology is based upon two distinct features; one is the use of a high quality compressive ZnO thin film, the other is the implementation of a floating electrode beneath the piezoelectric ZnO film in order to induce more strain in the diaphragm of the microspeaker when two top electrodes are biased with different polarities. A high quality piezoelectric ZnO film is achieved using an Ar/O 2 gas ratio of 4:1, an R.F. power of 1,500W, a substrate temperature of 150°C, and a chamber pressure of 23mTorr. In this condition, the deposited ZnO film shows a compressive residual stress of −1.3GPa. The fabricated piezoelectric microspeakers were tested over a frequency range of 400Hz to 12kHz with a 5V peak-to-peak input signal, the maximum SPL of the fabricated microspeakers was shown to be more than 97.2dB at 7.1kHz with a distance of 3mm between the fabricated microspeakers and the reference microphone (B&K type 2,669 and 4,192L).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.