Volume 95, Issue 10, 15 May 2004
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
95(2004); http://dx.doi.org/10.1063/1.1699500View Description Hide Description
The dynamics of polarization switching have been investigated over extremely broad time and field ranges for and -oriented crystals. The results demonstrate the presence of broad relaxation time distributions that can extend over a decade(s) in orders of magnitude in time, and which sharpen significantly with increasing field. The polarization transients have been fit to stretched exponential functions, which are typical of disordered systems.
95(2004); http://dx.doi.org/10.1063/1.1703829View Description Hide Description
Direct measurements of longitudinal and transverse piezoelectric coefficients have been made on cuboid samples of -poled (PZN-4.5PT) and (PMN-32PT) single crystals. The measurements were made in a Berlincourt-type press over a wide range of dynamic and static bias stresses. In the transverse mode, the response was found to be essentially anhysteretic and was independent of the dynamic stress amplitude. In contrast, for the longitudinal mode, the piezoelectriccharge-stress behavior is hysteretic. Moreover, the relative hysteresis size and the coefficient are both strong functions of bias stress, dynamic stress amplitude, and frequency; coupling of the dynamic stress dependency of to the charge-stresshysteresis is demonstrated by a quasi-Rayleigh-type relationship. The observed hysteretic response could be due to domain switching in the crystals although this would be unexpected for a -poled rhombohedral crystal. Instead, following the observed difference between transverse and longitudinal behaviors, it is suggested that polarization rotation away from the poling direction leads to a hysteretic response.
95(2004); http://dx.doi.org/10.1063/1.1699499View Description Hide Description
Simple multiferroic laminated ceramics of lead–zirconate–titanate were prepared by a conventional ceramic processing. The measured magnetodielectric properties demonstrated strong dependence on the relative thickness of the PZT layers, magnetic bias, and angle between the bias and polarization in the laminated ceramics. Recent theoretical approaches were employed to explain these observed behaviors. The maximum magnetoelectric sensitivity of the ceramics samples could reach up to as high as 0.21 V/A at 11.9 kA/m. In particular, at low magnetic bias, the laminated ceramics were found to have a very large magnetoelectric sensitivity linearly varying with the bias.
95(2004); http://dx.doi.org/10.1063/1.1711160View Description Hide Description
Manganese and samariumdoped lead titanate PSmT] fibers were prepared by sol-gel method. The micrographs obtained using scanning electron microscope show that PSmT ceramic fibers are round and dense. The diameter of the fibers was in the range of 30–35 μm. The crystalline grains size is ∼2.5 μm. The micrographs obtained using transmission electron microscope also unveiled the layer-by-layer 90° domains in the grains. X-ray diffraction patterns of the fibers show that PSmT ceramics have a pure perovskite structure. The ratio of the unit cell was 1.04. The PSmT fiber/epoxy 1-3 composites were fabricated by filling the ceramic fiber bundle with epoxy. The dielectric permittivity ε, electromechanical coefficient and the piezoelectric constant of PSmT fiber/epoxy 1-3 composites with 68% fiber loading were 118, 0.51, and 48 pC/N, respectively. The hysteresis loop of the composites was measured by the Sawyer–Tower method. It was also found that the composites could withstand an electric field of 15 kV/mm at room temperature.