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Abstract Ferroelectric films suffer from both aging and degradation under high ac‐field drive conditions due to loss of polarization with time. In this study, the roles of defect chemistry and internal electric fields on the long‐term stability of the properties of piezoelectric films were explored. For this purpose, lead zirconate titanate (PZT) films with a Zr/Ti ratio of 52/48 doped with Mn‐ (PMZT) or Nb‐ (PNZT) were deposited on Pt coated Si substrates by the sol‐gel method. It was demonstrated that the magnitude of the internal field is much higher in PMZT films compared to PNZT films after poling in the temperature range of 25‐200°C under an electric field of −240 kV/cm. The development of the internal field is thermally activated, with activation energies from 0.5 ± 0.06 to 0.8 ± 0.1 eV in Mn doped films and from 0.8 ± 0.1 to 1.2 ± 0.2 eV in Nb doped films. The different activation energies for imprint suggests that the physical mechanism underlying the evolution of the internal field in PMZT and PNZT films differs; the enhanced internal field upon poling is attributed to (a) alignment of oxygen vacancy—acceptor ion defect dipoles (,) in PMZT films, and (b) thermionic injection of electron charges and charge trapping in PNZT films. In either case, the internal field reduces back switching, enhances the remanent piezoelectric properties, and dramatically improves the aging behavior. PMZT films exhibited the greatest enhancement, with reduced high temperature (180°C) aging rates of 2%‐3%/decade due to improved stability of the poled state. In contrast, PNZT films showed significantly larger high temperature aging rates (15.5%/decade) in the piezoelectric coefficient, demonstrating that the fully poled state was not retained with time.
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Combined electromechanical dynamic fracture behavior of lead zirconate titanate (PZT)
Abstract Coupon specimens of poled and depoled lead zirconate titanate (PZT) are examined under combined stress wave and electric loading conditions. Mode‐I crack initiation and fracture behavior is examined using ultrahigh‐speed imaging and two‐dimensional digital image correlation. The dynamic critical stress intensity factor () is extracted using measured displacement fields ahead of the impulsively loaded crack tip, and compared between poled and depoled plates that were either under no electric field, positive 0.46 kV/mm electric field, or negative 0.46 kV/mm electric field. Poled specimens had a poling direction and applied electric field direction normal to the crack front. The addition of an electric field resulted in a crack‐enhancing effect, where the dynamic fracture toughness of poled specimens under0.46 kV/mm was almost half that of samples with no electric field. Depoled samples experienced almost no change in dynamic fracture toughness with the addition of an electric field.
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- Award ID(s):
- 1555015
- PAR ID:
- 10366752
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 105
- Issue:
- 5
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 3116-3122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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