Materials for Adaptive Structural Acoustic Control. Volume 5.
Annual rept. 1 Feb 95-31 Jan 96,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB
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This report documents work carried forward over the fourth year of a five year ONR sponsored University Research initiative URI entitled Materials for Adaptive Structural Acoustic Control. The program has continued to underpin the development of new electro-ceramic, single crystal and composite materials combinations for both the sensing and actuation functions in adaptive structures. For the lead based perovskite structure relaxer ferroelectric electrostrictors, new experimental and theoretical studies have underscored the critical role of nano-scale heterogeneity on either A or B sites of the ABO3 in promoting dispersive dielectric response and the very strong opposing role of elastic stress and electrostrictive coupling in suppressing polarization fluctuations. Most important for practical application is the regimen where, under high electric field nano-polar regions begin to amalgamate into ferroelectric macro-domains with very mobile walls lead to unusually large extrinsic piezoelectric coefficients. The program has explored a range of new relaxerferroelectric solid solutions which exhibit morphotropic phase boundaries between rhombohedral and tetragonal ferroelectric phases. Some of these compositions are much more tractable than PZT to grow in single crystal form. A major surprise is the very strong enhancement of the piezoelectric d33 and d31 in the crystal over that in the corresponding ceramic, and the massive anisotropy for different orientations and directions of poling. Optical studies suggest that the unusual effects reside largely in the extrinsic domain controlled response and we speculate about the mobility of walls in metastable phases, however further studies are required.
- *PIEZOELECTRIC TRANSDUCERS
- EXPERIMENTAL DATA
- ADAPTIVE CONTROL SYSTEMS
- COMPOSITE MATERIALS
- SINGLE CRYSTALS
- LEAD TITANATES
- FERROELECTRIC MATERIALS
- SOLID SOLUTIONS
- Ceramics, Refractories and Glass