Date: Thursday, Mar 4th
Presenter: Eric Patterson and Yu Hong Jeon, OSU Materials Science
Eric Patterson Abstract:
Development and Characterization of Lead-Free Piezoelectric Systems
ABSTRACT: Solid solutions based on Li, Ta, and Sb doped (K0.5Na0.5)NbO3 (KNN) lead-free perovskite systems were created using standard solid state methods. X-ray diffraction was used to confirm that all compositions were single phase. The three compositions examined, colloquially known as LF4, were shown to be strongly ferroelectric with sharp peaks in permittivity present at the Curie temperature. The composition LF4-2 had the best loss tangent values with tan delta less than 0.05 up to 100 kHz at room temperature. Bipolar hysteresis measurements showed high values for both maximum polarization (25 µC/cm^2) and remenant polarizations (20 µC/cm^2). The unipolar fatigue behavior was characterized by an initial drop in the maximum polarization over the first 10 cycles followed by a stable region which persisted to 100,000 cycles. Further unipolar fatigue testing on CuO doped LF4 samples was performed out to 1,000,000 cycles.
Yu Hong Jeon Abstract:
Piezoelectric Properties and Fatigue Behavior of Bi-based Lead Free Ceramics
ABSTRACT: Lead free piezoelectric ceramics, Bi(Zn0.5Ti0.5)O3-(Bi0.5K0.5)TiO3 (BZT-BKT) and (Bi0.5K0.5)TiO3?(Bi0.5Na0.5)TiO3 (BKT-BNT) solid solutions were investigated. xBZT-(1-x)BKT and yBKT-(1-y)BNT in the range of x=0.05 to 0.1 and y=0.16 to 0.2 showed tetragonal symmetry and a morphotropic phase boundary between rhombohedral and tetragonal symmetry. For BZT-BKT, the transition temperature decreased slightly with increasing BZT content but BZT-BKT maintained a high dielectric constant (K = 4,000) with low loss tangent at high temperatures. For BKT-BNT, two dielectric anomalies were observed. At lower temperatures (110 to 150 °C) a rhombohedral to tetragonal transition was observed. At approximately 300 °C, a dielectric maximum occurred corresponding to the Curie temperature. Hysteresis loops of two different solid solutions showed ferroelectric behavior with a high level of polarization, above 25 µC/cm^2 for BZT-BKT and 30 µC/cm^2 for BKT-BNT. Additionally, fatigue behaviors of both solid solutions were characterized.