Volume 92, Issue 4, 15 August 2002
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
Investigation of two-phase nucleation in paraelectric phase of ferroelectrics with ferroelectric–antiferroelectric–paraelectric triple point92(2002); http://dx.doi.org/10.1063/1.1493661View Description Hide Description
Results of investigation of phenomena preceding the phase transition from paraelectric to dipole-ordered phases in solid solutions with compositions close to the ferroelectric–antiferroelectric–paraelectric triple point in the Ti-concentration-temperature phase diagram are presented. X-ray diffraction and piezoelectric resonance methods are used for identification of the two-phase (antiferroelectric and ferroelectric) nuclei at the temperatures above the curie temperature. The relation between the presence of these two-phase nuclei in paraelectric phase of the compound and the diffuseness of the ordering phase transition is noted. The phenomenon of ion segregation at the interdomain boundary separating regions of ferroelectric and antiferroelectric phases and its role in enabling the observation of the piezoelectric resonance are discussed.
Effects of rare earth metal substituents on the piezoelectric and polarization properties of ceramics92(2002); http://dx.doi.org/10.1063/1.1490617View Description Hide Description
The piezoelectric properties of modified with the rare earth (RE)metal species Ce (1.03 Å), Eu (0.95 Å) and Yb (0.85 Å) have been investigated. For all rare earth substituents investigated in this system, regardless of the species ionic radii, the piezoelectric properties were observed to have combinatory hard and soft characteristics. Under high drive levels, the mechanical quality factor and the vibrational velocity were both significantly improved by RE substitution, resulting in a significant increase in ultrasonic power. Systematic polarization–electric field measurements revealed significant relaxational polarization similar to a soft piezoelectric, in addition to an internal field similar to a hard piezoelectric. A possible explanation for the combinatory “hardening” and “softening” effects is the coexistence of randomly quenched and mobile defects.
Structural and dielectric characterization of the thin films deposited on substrate by radio frequency magnetron sputtering92(2002); http://dx.doi.org/10.1063/1.1492002View Description Hide Description
thin films prepared by rf magnetron sputtering have been characterized as a function of temperature, applied voltage, and electric field. The thin films have been confirmed with x-ray diffraction and electron diffraction analysis. The thin films show a strong (111) preferred orientation for Sr content Grain size increases with increasing deposition temperature and is correlated to high dielectric constants. Leakage current density at 1 kV/cm varies from below to mid for the ratio varying from to A large and clear hysteresis shows ferroelectricity at 25 °C for all thin films. The remnant polarization increases with increasing Sr content, which is preseemably caused by the lattice mismatch between thin films and Pt layers.
92(2002); http://dx.doi.org/10.1063/1.1495894View Description Hide Description
Ferroelectric (PZSTN) thin films with different preferred orientations were fabricated by modifying with 20 mol % excess lead that contained a seed layer Ferroelectric properties were investigated in terms of the texturing character of the PZSTN thin film. With an increase in Zr content in the seed layer, the (100) texturing of the PZSTN film was enhanced. The highly (100) texture (∼97%) was developed by inserting a seed layer with between the Pt-coated substrate and the PZSTN thin film, whereas in the case of annealing in a reduced condition, the orientation of the film became nearly (111). The (111)-oriented PZSTN film showed relatively higher remanent polarization compared to that of the (100)-oriented film, while the (100)-oriented PZSTN film showed more fatigue behavior than the (111)-oriented film after switching cycles. The (111)-oriented PZSTN film with rhombohedral structure is believed to be suspected to significant stress along applied field direction, resulting in the production of many defects, causing degradation of the polarization during switching cycles.
92(2002); http://dx.doi.org/10.1063/1.1495531View Description Hide Description
The domain reorientation process in polycrystallinematerials was investigated through hysteresis loop measurements in soft and hard lead zirconate titanate(PZT) bulk ceramics. In order to investigate the degree of alignment of domains with the electric field the ferroelectric characterizations were performed in two perpendicular directions for each sample. It was found that for the soft PZT, the kinetics of the fatigue process due to space charges in a specific direction is not affected by the previous fatigue story induced in the other perpendicular one thus showing a fatigue anisotropy. This fact was attributed to no displacement of part of space charges during the electric field switching. However, for the hard PZT, an influence of the previous electric story could be observed due to the continuous realignment of the complex defects perpendicularly to the electric field.